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  • 1
    Digitale Medien
    Digitale Medien
    Parametrically induced light diffraction in crystals with second-order susceptibility (1995)
    Springer
    Applied physics 60 (1995), S. 421-426 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The theoretical description of parametric cascaded processes produced by intersecting beams in crystals with second-order susceptibility is presented. A common system of equations in the Slowly Varying Amplitude (SVA) approximation is used to treat the phenomenon. This approach provides a description of overall self-diffraction processes and the equations are well suited for numerical simulations. A relation between phase-matching conditions for parametric cascading processes and diffraction efficiency is found. Pump depletion influence is analysed. The results of numerical simulations are in good agreement with experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081321
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  • 2
    Digitale Medien
    Digitale Medien
    Odd and even two-dimensional dark spatial solitons (1995)
    Springer
    Applied physics 61 (1995), S. 121-124 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The formation of two-Dimensional (2D) odd dark spatial solutions is analyzed numerically at an initial helical dark-beam phase distribution. Experimental results are presented for the first time confirming the existence of two-dimensional optical even dark solitons (ring dark solitons). Several aspects of the evolution of input 1D and 2D odd/even dark beams are compared qualitatively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090982
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  • 3
    Digitale Medien
    Digitale Medien
    Generation of 6.8–7.7 µm radiation in lithium iodate (1995)
    Springer
    Applied physics 61 (1995), S. 489-491 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 63.20 ; 78.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Generation of infrared radiation in ts-infrared transmission window (6.8–7.7 µm) is reported for the first time by non-collinear difference-frequency mixing of the Nd: YAG second harmonic and the same-pumped dye (Rh-610) laser radiation in a lithium-iodate crystal. The spectrum of polythene sheets was run with the generated radiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081278
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  • 4
    Digitale Medien
    Digitale Medien
    Effect of three-wave-phase development on the stimulated Raman scatttering in an electron plasma (1996)
    Springer
    Applied physics 62 (1996), S. 309-311 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 52.40 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The effects of the development of the three-wave phase on the amplitude of the pumping laser light, the scattered light, and the electron plasma wave are studied. Analytical solutions are obtained to describe a pumping laser light decreasing with time and the development of the electron plasma wave and scattered wave from an initial increasing state to saturation and finally to a decaying state which is closely related to the three-wave phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080961
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  • 5
    Digitale Medien
    Digitale Medien
    Birth and evolution of wave-front dislocations in a laser beam passed through a photorefractive LiNbO3: Fe crystal (1996)
    Springer
    Applied physics 62 (1996), S. 465-471 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on an experimental and numerical investigation of the process of spontaneous optical vortices nucleation in a wave front of a laser beam passed through a photorefractive LiNbO3 : Fe crystal with self-induced nonlinear lens. The complex lens structure produces mainly defocusing of the beam passing through the crystal due to a negative variation of the refractive index, whereas side parts of the lens have a positive sign of refractive-index variation and partially focus the beam. The resulting wave-front distortions lead to a phase bifurcation occurring at a certain distance after the crystal when the amplitude of the light wave becomes zero. We study in detail the process of edge dislocation nucleation and its decay in the near field producing a pair of unity-charged opposite-sign screw dislocations. After birth, they spread along dislocation axes as stable objects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081045
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  • 6
    Digitale Medien
    Digitale Medien
    Excited-state absorption and third-order optical nonlinearities in symmetric π-electron organic molecules (1996)
    Springer
    Applied physics 63 (1996), S. 47-50 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 31.20.Nt ; 42.65 ; 42.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Excited-State Absorption (ESA), Two-Photon Absorption (TPA) and the third-order polarizability γ(ω;ω,ω, − ω) have been investigated for a model dichloride derivative of a symmetrically substituted benzylidene analine (SBAC), using a multielectron configuration-interaction procedure. The calculations indicate that SBAC exhibits ESA across the visible region of the spectrum, but that it is not as extensive as for molecules such as the phthalocyanines. The magnitude of the third-order polarizability is dominated by resonance enhancement from a very strongA g →B u one-photon absorption. The calculated off-resonance value for γ(ω;ω,ω, − ω) suggests that SBAC is a potential candidate for ultrafast switching applications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01112837
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  • 7
    Digitale Medien
    Digitale Medien
    Generation of high-order rotational lines by four-wave Raman mixing using a high-power picosecond Ti:Sapphire laser (1996)
    Springer
    Applied physics 63 (1996), S. 121-124 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 51.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract More than thirty rotational lines equally spaced by 587 cm−1 are generated simultaneously in the vicinity of the fundamental line by four-wave Raman mixing using a high-power picosecond Ti:Sapphire laser as a pump source and hydrogen as a Raman medium. Since the wavelength of this multifrequency laser emission extends from the near-infrared to the near-ultraviolet, it can be utilized as a tunable light source for picosecond spectroscopy. Because of the wide spectral bandwidth available, this procedure has great potential for the generation of ultrashort laser pulses by mode-locking these emission lines.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01095260
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  • 8
    Digitale Medien
    Digitale Medien
    Photorefraction in the ultraviolet: Materials and effects (1995)
    Springer
    Applied physics 61 (1995), S. 351-360 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.25.Bs ; 42.65 ; 78.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Doped as well as nominally pure crystals of Lithium Niobate (LiNbO3), ι-Arginine Phosphate (LAP), Lithium Iodate (LiIO3), Potassium Dihydrogen Phosphate (KDP), Lithium Formate (LFM), Beta-Barium Borate (BBO), and lithium tetra borate were grown and investigated for photorefractive effects at ultraviolet wavelengths down to 333 nm. In nominally undoped LiNbO3 crystals strong beam coupling effects were observed. In contrast to the visible we revealed a diffusion-dominated charge transport mechanism based on holes, and a low photovoltaic field in the order of 550 V/cm. With such a crystal we investigated the modulation transfer function of a lensless image projection system based on a phase conjugation scheme. A spatial frequency response beyond 2800 line pairs per millimeter was observed. Photorefractive beam coupling was also obtained in LiIO3. Light-induced scattering was detected in iron-doped LiIO3 whereas as-grown LAP material did not exhibit any observable photorefractive effects. However, 100 kV X-ray irradiation seems to induce material defects which can lead to weak light-induced scattering at 351 nm. In all other above-mentioned materials, doped as well as undoped, light-induced scattering could not be observed. On the other hand, this is appreciated in all the applications where the crystals are used as nonlinear material for optical frequency conversion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081535
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  • 9
    Digitale Medien
    Digitale Medien
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 429-437 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We systematically investigate the difference between both actively and passively mode-locked lasers with Gain-at-the-End (GE) and Gain-in-the-Middle (GM) at the example of Nd:YLF lasers. The GE laser generates pulse widths approximately three times shorter than a comparable GM cavity. This is due to enhanced Spatial Hole Burning (SHB) which effectively flattens the saturated gain and allows for a larger lasing bandwidth compared to a GM cavity. We first investigate enhanced SHB by measuring the cw mode spectrum, where we have observed that the mode spacing in GE cavities depends primarily on the crystal length. This was also confirmed for a Nd:LSB crystal, where the pump absorption length was significantly shorter than the crystal length. In mode-locked operation, pulse widths of 4 ps for passive mode locking and 5 ps for active mode locking are demonstrated with GE cavities, compared to 11 ps for passive and 17 ps for active mode locking with GM cavities. Additionally, the time-bandwidth product for the GE cavity is approximately twice the ideal product for a sech2 pulse shape and cannot be improved by dispersion compensation alone, while the GM cavity has nearly ideal time-bandwidth-limited performance. The results for the GM cavity compare well to existing theories taking into account the added effect of pump-power-dependent gain bandwidth which increases the bandwidth of Nd: YLF from 360 to 〉 500 GHz. In a following paper [1] (called Part II) a rigorous theoretical treatment of the effects due to SHB will be presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081271
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  • 10
    Digitale Medien
    Digitale Medien
    Shot-by-shot frequency calibration of CARS spectra: Application to the measurement of the collisional line shift in oxygen (1996)
    Springer
    Applied physics 62 (1996), S. 521-525 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.60 ; 42.65 ; 33.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A technique using a Fabry-Perot interferometer has been developed to calibrate high-resolution spectra obtained by Coherent Anti-Stokes Raman Spectroscopy (CARS). This technique was used to measure simultaneously the Raman frequency and the Raman signal at each laser shot. We demonstrate the accuracy of the method by measuring theQ(15) line shifts of molecular oxygen due to collisions with oxygen and water vapour.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081054
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  • 11
    Digitale Medien
    Digitale Medien
    Two-photon excitation of atomic oxygen using a Raman-shifted ArF-excimer laser (1995)
    Springer
    Applied physics 60 (1995), S. 61-65 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 32.00 ; 42.65 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A novel method for exciting the two-photon 2p 3 3p 3 P ←2p 4 3 P atomic oxygen transition is reported. The transition energy is provided by the combined photon energies of the second and third Stokes orders of a deuterium-filled Raman shifter pumped by an ArF-excimer laser. The ArF-excimer-pumped Raman shifter performance is characterized and the approach is demonstrated in an atomic oxygen population created by molecular oxygen absorption and predissociation in room air.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082074
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  • 12
    Digitale Medien
    Digitale Medien
    SBS mirrors for XeCl lasers with a broad spectrum (1995)
    Springer
    Applied physics 61 (1995), S. 73-80 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.60. Da
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The stimulated Brillouin scattering threshold of focused broad-band XeCl laser radiation depends on the ratio of the coherence length to the Rayleigh range, which is affected by the transverse beam quality. With reduction of the focal length, the threshold decreases first and then reaches a nearly constant value. In addition, the energy reflectivity is increased. On the other hand, pulse shortening occurs and the phase conjugation fidelity is decreased. Separation of single lines from the structured XeCl laser spectrum improves the SBS efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090975
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  • 13
    Digitale Medien
    Digitale Medien
    Three-photon absorption and its limitation of third-order nonlinear optical effects in rutile (1995)
    Springer
    Applied physics 61 (1995), S. 127-134 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.65 ; 78.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Three-photon absorption and three-photon-induced excited-state absorption of rutile are studied by transmission measurements using picosecond pulses of a mode-locked Nd: glass laser. The nonlinear absorption limits efficient stimulated Raman scattering. It reduces the efficiency of two-photon absorption of a picosecond probe continuum. Three-photon absorption coefficients, excited-state absorption cross sections, a Raman gain factor, and two-photon absorption cross-section spectra are determined. The arrangementsE⊥c andE ∥c are considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090933
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  • 14
    Digitale Medien
    Digitale Medien
    Characterization of the KNSBN: Cu crystal with two-wave coupling at visible and infrared wavelengths (1995)
    Springer
    Applied physics 61 (1995), S. 207-211 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.70.Gz ; 42.30.Va ; 42.40.Kw ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have optically characterized the newly-developed photorefractive crystal KNSBN: Cu by two-wave coupling at visible and near-infrared wavelengths. The effective electrooptic coefficientsξ(k g)r 13 andξ(k g)r 33, the effective charge carrier densityN eff, the dark conductivityσ d, the product of mobility and electron-trap recombination timeμτ R, the formation and decay rate of index grating and the absorption coefficientα of the crystal were determined from visible to near-infrared wavelengths. Their wavelength dependences were also studied. It is interesting to notice that the KNSBN: Cu crystal has a very largeN eff and large gain coefficientΓ for ordinary ray (o-ray) in the visible region, and the photorefractive properties of the crystal are very different in the visible and near-infrared spectral regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090945
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  • 15
    Digitale Medien
    Digitale Medien
    Development of a dual-wavelength dye-laser system for the UV and its application to simultaneous multi-element detection (1995)
    Springer
    Applied physics 61 (1995), S. 339-343 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.65 ; 82.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper, the design and performance characteristics of a pulsed tunable dye laser system for the simultaneous generation of two UV wavelengths are presented. The system is composed of an oscillator and an amplifier stage, pumped by the second harmonic of a commercial Nd:YAG laser. Dual-wavelength operation is achieved with one additional tuning mirror introduced to the prism expanded grazing incidence oscillator. The two obtained wavelengths are independently tunable, their separation is only limited by the gain profile of the dye. Both wavelengths are frequency doubled by Second-Harmonic Generation (SHG) in two KDP or BBO crystals. Performance characteristics such as bandwidth, efficiency, tuning range and wavelength separation are reported. As application two such systems are used for the simultaneous detection of the four elements cadmium, nickel, manganese and lead by Laser-Excited Atomic Fluorescence Spectrometry in a graphite furnace (ETA-LEAFS).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081533
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  • 16
    Digitale Medien
    Digitale Medien
    Thermometry of an oxy-acetylene flame using multiplex degenerate four-wave mixing of C2 (1996)
    Springer
    Applied physics 62 (1996), S. 39-44 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 33.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Thermometry of an oxy-acetylene flame using multiplex Degenerate Four-Wave Mixing (DFWM) of C2 is demonstrated. More than 100 rotational transitions in thed 3 Π g ←a 3 Π u (0,0) Swan band of C2 could be recorded simultaneously by use of a pulsed, broad bandwidth “modeless” laser. Temperatures were inferred by fitting temperature-dependent synthetic spectra of single- or multiple-shot averaged spectra. The strength and reliability of recorded signals together with the large number of rotational lines observed suggest that multiplex DFWM is a promising technique for minor species detection and for temporally resolved temperature measurements in luminous environments. Factors influencing the accuracy and precision of single-shot thermometry using the technique are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081245
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  • 17
    Digitale Medien
    Digitale Medien
    Optical restoration of photorefractive holograms (1995)
    Springer
    Applied physics 61 (1995), S. 511-514 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.30 ; 42.40 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the possibility of restoration and/or enhancement of decaying holograms in photorefractive media by using a simple optical readout in conjunction with a phase conjugator. The results indicate that extremely weak holograms can be enhanced provided that the two-beam coupling is sufficiently strong. Steady-state photorefractive holograms can be maintained continuously without decay by using a self-enhanced readout scheme. The results also provide an explanation for the formation of mutually pumped phase conjugation in terms of the amplification of an initial noise grating. The results are presented and discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081282
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  • 18
    Digitale Medien
    Digitale Medien
    Design of a compact blue-green stimulated hydrogen Raman shifter (1996)
    Springer
    Applied physics 62 (1996), S. 479-483 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 78.30 ; 78.32 ; 42.70 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A design of a compact blue-green stimulated Raman shifter pumped by the third harmonic of a Nd:YAG laser is presented. Design parameters given here are based on our experimental investigation of various optimization techniques involving parametric studies. Blue-green energy conversion of up to 66% is achieved. The problem of optical breakdown is addressed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081047
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  • 19
    Digitale Medien
    Digitale Medien
    Temperature measurements in CO2-laser-induced pyrolysis flames for SiC and ternary SiC/C/B powder synthesis by means of CARS (1996)
    Springer
    Applied physics 62 (1996), S. 609-612 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 36.40 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The hot luminescent reaction zones of CO2-laser-induced pyrolysis flames using SiH4/C2H2 gas mixtures with different silane to acetylene ratios and with and without diborane additives were investigated by means of H2 Q-branch CARS spectroscopy, leading to spatial temperature profiles in gas flow direction. In the case of B2H6 additive to the stoichiometric SiH4/C2H2 mixture a high temperature plateau (≈ 800–1000 K) of the reactant gas volume develops already several millimetres before reaching the CO2-laser focus line. This precursor preheating zone could be explained by the catalytic effect of boron atoms or boron-containing intermediate species in the flame. A similar behaviour for acetylene-rich flames operating at half laser power was not observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081699
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  • 20
    Digitale Medien
    Digitale Medien
    Parallel guiding of signal beams by a ring dark soliton (1996)
    Springer
    Applied physics 63 (1996), S. 145-150 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Guiding of multiple signal beams in an induced all-optical cable is studied theoretically. A balance relation is derived for the interaction geometry and undistorted propagation of bright elliptical signal beams nested in a single ring dark soliton. The numerical analyses show a remarkable misalignment stability of the parallel guiding scheme.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01095265
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  • 21
    Digitale Medien
    Digitale Medien
    Grating feedback in a 810 nm broad-area diode laser (1996)
    Springer
    Applied physics 63 (1996), S. 117-120 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60B ; 42.60D ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Narrow linewidth, single spectral mode operation has been obtained in a high power, 810 nm broad-area diode laser in an extended cavity configuration with a grating as external reflector (grating feedback). For stable operation it was necessary to misalign the feedback slightly in the plane of the laser junction. Characteristics of the thus obtained laser system are a linewidth below 5 MHz, an output intensity of about 50% of the free running power, a large-scale tuning range of 15 nm and continuous scanning over 4 GHz. In the spatial domain, the laser remains multimode and astigmatic. To show the practical applicability of this system, saturated absorption of a krypton line is demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01095259
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  • 22
    Digitale Medien
    Digitale Medien
    The effect of mid-infrared and far-infrared emission, generated at NH3 excitation by intense radiation of a TEA CO2 laser, on ammonia absorption (1996)
    Springer
    Applied physics 63 (1996), S. 355-361 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 33.00 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The effect of Mid-InfraRed (MIR) (λ ≅ 12 μm) and Far-InfraRed (FIR) (λ ≽ 100 μm) emission from excited ammonia on the absorption of intense radiation of a TEA CO2 laser has been studied experimentally under collisional and collisionless excitation conditions with ammonia pressures from 0.5 to 0.03 Torr. The energy of MIR and FIR emission was studied as a function of NH3 pressure and laser energy fluence. Particular emphasis was given to the kinetics of MIR and FIR emission generation at different NH3 pressures and to the measurement of the time delay of re-emitted pulses relative to the exciting CO2 laser pulse. It has been found that the re-emission in the MIR range is highly collisional in nature. The intensity of MIR emission drops sharply (asp 3) with decreasing NH3 pressure and its delay time relative to the exciting laser pulse increases. At the same time, re-emission in the FIR range (in the case of resonant excitation of NH3 at the 9R (30) line of CO2 laser) is observed during an exciting pulse up top 〈 0.03 Torr. When binding the rotational sub-levels of a molecule with transitions, FIR emission acts as rotational relaxation and thus leads to an increase in NH3 IR absorption even at collisionless excitation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01828738
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  • 23
    Digitale Medien
    Digitale Medien
    A continuously tunable long-wavelength cw IR source for high-resolution spectroscopy and trace-gas detection (1996)
    Springer
    Applied physics 63 (1996), S. 437-441 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 7.65 ; 33.00 ; 42.60 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new widely tunable source in the infrared for use in high-resolution spectroscopy and trace-gas detection is described. This spectroscopic source is based on Difference Frequency Generation (DFG) in gallium selenide (GaSe) and is continuously tunable in the 8.8–15.0 μm wavelength region. Such a DFG source operates at room temperature which makes it a useful alternative to a lead-salt diode-laser- based detection system that requires cryogenic temperatures and numerous individual diode lasers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01828938
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  • 24
    Digitale Medien
    Digitale Medien
    H2 CARS thermometry in a fuel-rich, premixed, laminar CH4/air flame in the pressure range between 5 and 40 bar (1995)
    Springer
    Applied physics 61 (1995), S. 49-57 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 33.20 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract To establish H2 CARS thermometry at high pressure, accumulated H2 Q-branch CARS spectra were recorded in the exhaust of a fuel-rich CH4/air flame at pressures between 5 and 40 bar. Temperatures were deduced by fitting theoretical spectra to experimental data points. The Energy-Corrected Sudden (ECS) scaling law was employed to set up an empirical model for the calculation of H2 linewidths in high-pressure hydrocarbon flames with H2 as a minority species. Experimental H2 CARS spectra could be simulated very accurately with this model. The evaluated temperatures agreed well with reference temperatures obtained by spontaneous rotational Raman scattering of N2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090971
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  • 25
    Digitale Medien
    Digitale Medien
    Origin of the resonant optical Kerr nonlinearity in Cd(S, Se)-doped glasses and related topics (1995)
    Springer
    Applied physics 61 (1995), S. 17-26 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract After having reported preliminary results related to saturation, we first theoretically consider the various mechanisms contributing to the resonant optical Kerr effect in Cd(S, Se)-doped glasses. We obtain the expression for the expected effective susceptibility in different possible cases. This nonlinearity is studied experimentally using optical-phase conjugation in the low-intensity regime. We show that, by time resolving the nonlinear response of such glasses having experienced various degrees of photodarkening, we can clearly assess the origin of the resonant optical Kerr effect in these materials. Usually, a combination of a fast free-carrier contribution due to particles without traps and of a slow trapped-carrier one due to particles with traps is observed. For the free-carrier contribution, induced absorption is observed to be almost as important as absorption saturation. We also report frequency-dependent measurements and discuss the change in absorption spectrum and the increase of the nonradiative decay rate that accompany darkening.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090967
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  • 26
    Digitale Medien
    Digitale Medien
    High-efficiency multicolour Q-switched Nd3+:KGd(WO4)2 laser (1995)
    Springer
    Applied physics 61 (1995), S. 213-215 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Energy output of 400 mJ, an order of magnitude higher than reported previously is obtained in aQ-switched flashlamp-pumped Nd3+:KGd(WO4)2 laser. No pronounced saturation of the output energy with respect to the pump energy is observed. Multiwavelength operation due to efficient Stokes conversion in the laser crystal is demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090946
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  • 27
    Digitale Medien
    Digitale Medien
    Efficient vacuum-ultraviolet generation by anti-Stokes Raman scattering using a cryogenic Raman cell (1995)
    Springer
    Applied physics 61 (1995), S. 319-323 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.55 ; 07.60 ; 07.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have investigated the increase of efficiency for high-order anti-Stokes Raman scattering using a cryogenic Raman cell. By cooling the cell to liquid-nitrogen temperature, output energies of the 9th-order anti-Stokes wave at 133 nm in normal hydrogen were enhanced by a factor of 10, and the 11th-order anti-Stokes line at 141 nm in normal deuterium appeared, while no output was observed at room temperature. No output energy enhancement, however, was obtained using cooled para-hydrogen as a result of multiple rotational Raman scattering. For long-term operation, the output window surface of the Raman cell was kept at above 200 K in order to protect it from deposition, the absorption of which is detrimental to VUV transmission.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081530
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  • 28
    Digitale Medien
    Digitale Medien
    Multiwave-pumped mirrorless parametric oscillation in BaTiO3 (1995)
    Springer
    Applied physics 61 (1995), S. 415-419 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 72.40 ; 78.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on the observation of mirrorless oscillation in photorefractive BaTiO3 pumped by two pairs of two nearly counterpropagating light waves, each of them containing an ordinary and an extraordinary component of polarization. The oscillation waves are located on a cone with an apex angle defined by the phase-matching conditions of this process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081269
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  • 29
    Digitale Medien
    Digitale Medien
    Ti:Sapphire-pumped femtosecond optical parametric oscillators based on KTiOPO4 and RTiOAsO4 (1995)
    Springer
    Applied physics 60 (1995), S. 437-442 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The design, configuration and operation of Ti:Sapphire-laser-pumped femtosecond Optical Parametric Oscillators (OPOs) using KTP and RTA are described. The results presented include configurations capable of producing transform-limited pulses shorter than 40 fs and operating with pump powers as low as 50 mW. Tunability within the 1–3 µn spectral region is demonstrated using pump-tuning alone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081323
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  • 30
    Digitale Medien
    Digitale Medien
    Visible femtosecond pulses by second-harmonic generation of a cw mode-locked KTP optical parametric oscillator (1995)
    Springer
    Applied physics 60 (1995), S. 453-458 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Efficient generation of femtosecond pulses in the wavelength range from 520 to 675 nm by external frequency doubling the signal wave of a non-critically phase-matched picosecond KTP Optical Parametric Oscillator (OPO) in a non-critically phase-matched temperature tuned LiB3O5(LBO) crystal is demonstrated. An average power of the second harmonic as high as 310 mW at 575 nm was generated. In the absence of group velocity mismatch of LBO for a wavelength of the OPO at about 1.3 µm the minimum second-harmonic pulse width was 400 fs at 645 nm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081326
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  • 31
    Digitale Medien
    Digitale Medien
    Four-photon parametric processes pumped by optical pulses with noise structure (1995)
    Springer
    Applied physics 60 (1995), S. 571-572 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 72.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A theoretical model of a transient nonlinear four-photon interaction in a fibre is proposed. An optimization of the efficiency of the parametric conversion is suggested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080937
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  • 32
    Digitale Medien
    Digitale Medien
    CARS thermometry in a transversely heated graphite-tube atomizer used in atomic absorption spectrometry (1995)
    Springer
    Applied physics 61 (1995), S. 201-205 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An experimental setup for gas-temperature diagnostics using Coherent Anti-Stokes Raman Scattering (CARS) in very small sample volumes with great spatial and temporal temperature variations is presented. Studies have been started of a newly designed transversely heated graphite-tube atomizer for atomic absorption spectrometry (Perkin-Elmer, 4100 ZL). For the investigations, high spatial resolution and precise time synchronization of the measurements and also automatic control of the time-dependent intensity of the anti-Stokes signal were realized. The graphite-tube atomizer also offers the possibility of high-temperature-gas spectroscopy. A high-temperature CARS spectrum of CO2, recorded in the graphite tube at 2300 K, is shown for the first time. A number of hot-band transitions in the spectral region of the Fermi doublet at a Raman shift from 1230 to 1450cm−1 was observed and assigned, making possible the use of CO2 as “spectroscopic thermometer gas”, similar to N2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090944
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  • 33
    Digitale Medien
    Digitale Medien
    Polarization-spectroscopic measurement and spectral simulation of OH (A 2 Σ−X 2 Π) and NH (A 3 Π−X 3 Σ) transitions in atmospheric pressure flames (1995)
    Springer
    Applied physics 61 (1995), S. 421-427 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 33.00 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Polarization spectroscopy has been used to investigate the electronic bands of OH (A 2 Σ-X 2 Π) and NH (A 3 Π-X 3 Σ) radicals generated in atmospheric pressure flames. The pump-beam intensity dependence of the polarization-spectroscopy signals of isolated lines in theR branches has been studied. It was found that significant saturation is noticeable for pump-beam intensities as low as 0.1 MW/cm2. A detailed theoretical description inluding laser-bandwidth convolutions has been developed to model unsaturated polarization spectra of OH and NH. For OH, temperature evaluations have been performed in methane/air flames from fits to experimentalR 1 band head spectral structures. The results are critically dependent on the degree of saturation in experimental spectra, instrumental bandwidth and the assumed coupling cases in the calculation of line-strength parameters. It is shown that saturation leads to an error of more than 60% in the temperature evaluation when a pump-beam intensity of 1 MW/cm2 is used.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081270
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  • 34
    Digitale Medien
    Digitale Medien
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 569-579 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In Part I of this paper [1] experimental results were presented and discussed. In this part, we investigate theoretically the dynamics of end-pumped solid-state lasers due to enhanced spatial hole burning. This becomes possible by a fast numerical implementation of the saturated gain in the presence of strong spatial hole burning that allows to treat the multimode case for an arbitrary pumping level. We find for a wide range of laser parameters that the mode spacing of the cw running modes is essentially determined by the length of the gain medium and only weakly depends on the absorption depth of the pump transition. It is shown that spatial hole burning can lead to a completely flat saturated gain profile over half of the gain bandwidth. In mode-locked lasers, the flat gain due to spatial hole burning results in shorter pulses. But the pulses are neither Gaussian-nor sech-shaped as they are in actively or passively mode-locked lasers without spatial hole burning. Further, we show that soliton-like pulse shaping can be used to restore a transform-limited sech-shaped pulse in an end-pumped solid-state laser while exploiting the full gain bandwidth of the laser material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01091215
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  • 35
    Digitale Medien
    Digitale Medien
    Relation of pump-beam quality and conversion efficiency in the Raman downward conversion (1996)
    Springer
    Applied physics 62 (1996), S. 59-64 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.65 ; 78.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract To investigate the full conversion of pump power to the Stokes waves in stimulated Raman scattering with a single-pass cell, unconverted pump energies have been analyzed in detail in relation to the first Stokes, second Stokes and first anti-Stokes energies. Adoption of a long focusing configuration with a high-pressure cell was found to be effective but insufficient to suppress the four-wave mixing effect, because a small amount of pump energy always remained undepleted. Comparison of the results using pump beams of various spectral and spatial mode characteristics from alexandrite and Nd:YAG lasers revealed that the spatial mode quality was the most critical parameter for full depletion of a pump pulse.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081248
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  • 36
    Digitale Medien
    Digitale Medien
    Phase measurements of ring dark solitons (1996)
    Springer
    Applied physics 62 (1996), S. 139-142 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A four-frame technique for interferogram analysis is used to measure the transverse phase distribution of nonlinearly split 2D dark beams. Pairs of diametrical phase shifts within each ring are retrieved from the experiment. This result is one of the tests required to denote the formations observed as ring dark solitons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081115
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  • 37
    Digitale Medien
    Digitale Medien
    Reverse saturable absorption and optical limiting in indanthrone dyes (1996)
    Springer
    Applied physics 62 (1996), S. 293-297 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.10 ; 42.65 ; 42.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Fluence dependence of transmission in three dyes, viz. indanthrone, dichloroindanthrone and violanthrone, is reported at 532 nm as well as at 1.06 µm. These dyes show optical limiting at both these wavelengths for nanosecond pulses. The limiting is due to the combined effect of reverse saturable absorption from the triplet state and thermal defocussing in the dye solutions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080958
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  • 38
    Digitale Medien
    Digitale Medien
    Polarization spectroscopy applied to C2 detection in a flame (1995)
    Springer
    Applied physics 60 (1995), S. 5-10 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 33.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The detection of C2 radicals in a premixed acetylene-oxygen flame by using polarization spectroscopy is reported. The signal was recorded in the Swan system,d 3 II g−a 3 II u (0, 0), using a pulsed dye laser. The spectrum shows a very good signal-to-noise ratio with clearly resolved rotational structures of theP andR triplets. The dependence of the signal on the pump-beam polarization was also studied. The spatial distribution of the signal from C2 radicals in the flame was measured as a demonstration of the use of polarization spectroscopy in combustion diagnostics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082066
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  • 39
    Digitale Medien
    Digitale Medien
    Single-valued determination of second-order nonlinear susceptibilities by quarter-wave-plate rotation (1995)
    Springer
    Applied physics 61 (1995), S. 135-141 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present a new technique to determine the complex-valued tensor components of the nonlinear surface susceptibility χ s (2) of isotropic adsorbate layers. It is based on a change of the state of the fundamental polarization by rotation of a quarter-wave plate. We verify the theoretical predictions by measurements on a Langmuir-Blodgett film of a highly nonlinear hemicyanine dye in total reflection geometry. The obtained second-harmonic rotation pattern is analyzed in Fourier components, which are related to the absolute value and relative phase of the tensor components of the surface susceptibility. We compare the obtained results with separate measurements in which a half-wave plate is used to rotate the fundamental polarization. Our results are confirmed by an additional interference experiment. The method presented here allows the single-valued determination of χ s (2) with measurements at only one angle of incidence, in contrast to the half-wave-plate technique.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090934
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  • 40
    Digitale Medien
    Digitale Medien
    Detection of methane in air using diode-laser pumped difference-frequency generation near 3.2 μm (1995)
    Springer
    Applied physics 61 (1995), S. 553-558 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.65 ; 33.00 ; 42.60 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Spectroscopic detection of the methane in natural air using an 800 nm diode laser and a diode-pumped 1064 nm Nd:YAG laser to produce tunable light near 3.2 µm is reported. The lasers were pump sources for ring-cavity-enhanced tunable difference-frequency mixing in AgGaS2. IR frequency tuning between 3076 and 3183 cm−1 was performed by crystal rotation and tuning of the extended-cavity diode laser. Feedback stabilization of the IR power reduced intensity noise below the detector noise level. Direct absorption and wavelength-modulation (2f) spectroscopy of the methane in natural air at 10.7 kPa (80 torr) were performed in a 1 m single-pass cell with 1 µW probe power. Methane has also been detected using a 3.2 µm confocal build-up cavity in conjunction with an intracavity absorption cell. The best methane detection limit observed was 12 ppb m (Hz.)−1/2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01091213
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  • 41
    Digitale Medien
    Digitale Medien
    Oxygen concentration and temperature measurements in N2–O2 mixtures using rotational coherent anti-Stokes Raman spectroscopy (1996)
    Springer
    Applied physics 62 (1996), S. 29-37 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 33.10 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The accuracy and precision of oxygen concentration and temperature measured by dual-broadband rotational Coherent Anti-Stokes Raman Spectroscopy (CARS) were investigated in nitrogen-oxygen mixtures at atmospheric pressure and temperatures between 290 and 1410 K. The relative standard deviation of temperatures evaluated from pure oxygen rotational CARS spectra was found to be around 5%, and the mean temperature was the same as for nitrogen CARS spectra, except for temperatures above 1000 K, where the temperature was 120 K below the correct value. The in situ calibrated oxygen concentrations were within 10% of the correct value, with a standard deviation of around 1.2% for the mixtures of 12 and 20% oxygen in nitrogen. For the lowest oxygen concentrations considered in this study (2 and 4%), the systematic errors in the evaluated concentrations were very large, and the standard deviation of repeated single-shot measurements was above 2%. However, employing weighting in the spectral fitting routine reduced the errors in the concentration and the single-shot standard deviation was lowered to 0.5%. Finally, it was shown that spectral interference (from oxygen) in a rotational CARS spectrum of nitrogen generally had little impact on the temperature evaluated from fitting the spectra to theoretical nitrogen spectra.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081244
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  • 42
    Digitale Medien
    Digitale Medien
    Degenerate four-wave mixing based on excited-state absorption in azo-dye-doped polymer films (1996)
    Springer
    Applied physics 62 (1996), S. 299-302 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.30 ; 42.65 ; 42.70 ; 42.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Degenerate Four-Wave Mixing (DFWM) based on excited-state absorption in azo-dye doped polymer films is firstly reported. Under a pre-exciting argon laser at 514.5 nm, DFWM is performed using a 632.8 nm HeNe laser which is absorbed only slightly when the molecules are in the ground state. The dynamic behavior of the DFWM signal due to excited-state absorption is also treated theoretically.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080959
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  • 43
    Digitale Medien
    Digitale Medien
    Split-step fourier methods applied to model nonlinear refractive effects in optically thick media (1996)
    Springer
    Applied physics 62 (1996), S. 389-397 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 02.60.Cb ; 02.70.-c ; 42.10 ; 42.25.Bs ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe and example the Beam Propagation Method (BPM) used to model and simulate nonlinear refractive and absorptive effects in materials with applications to optical limiting and switching. Various scenarios including laser-beam trapping and laser-beam division are investigated, in order to demonstrate the power of the BPM. A novel technique is also described for efficiently modelling the external far-field propagation from nonlinear media, including the propagation of non-Gaussian-shaped spatial profiles. The methods are finally combined with the phenomenon of nonlinear absorption to demonstrate enhanced power limiting in the presence of self-refraction. Optimal parameters for high-fluence power-limiting are subsequently discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081201
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  • 44
    Digitale Medien
    Digitale Medien
    Analytical formulae for the optimization of the process of low-power phase modulation in a quadratic nonlinear medium (1996)
    Springer
    Applied physics 63 (1996), S. 39-42 
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    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We show that using the approximation of fixed intensity analytical formulae, describing the process of induced phase modulation for the beams involved in second-order nonlinear optical processes can be derived. Expressions that allow the optimization of the phase shifts experienced by the fundamental and generated waves are presented for nonlinear quadratic processes, second-harmonic generation and sum-frequency mixing. In the case of seeding at the generated wavelength, the phase shift of the fundamental wave is due to two interactions: (i) a cubic one, based on coupled second-order processes (cascade cubic nonlinearity) and (ii) single quadratic interaction with participation of the seeding wave. By comparison with the exact numerical solution, we defined the input parameters of the beams for which this analytical approach is valid. It is shown that phase shifts exceeding π/2 can be correctly predicted using the expressions obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01112835
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  • 45
    Digitale Medien
    Digitale Medien
    Mixing of 30 THz laser radiation with nanometer thin-film Ni-NiO-Ni diodes and integrated bow-tie antennas (1996)
    Springer
    Applied physics 63 (1996), S. 135-140 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.62 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Mixing experiments with 30 THz CO2-laser radiation as well as the detection of 35 ps 30 THz pulses of an optical-free-induction-decay CO2-laser system have been performed with the first nanometer thin-film Ni-NiO-Ni diodes with a minimum contact area of 0.012 µm2. Difference frequencies up to 85 MHz were detected by mixing two different CO2-laser beams coupled to the diode with an integrated bow-tie antenna. The dependence of the beat signal on bias voltage, laser power and polarization of the infrared laser radiation was determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01095263
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  • 46
    Digitale Medien
    Digitale Medien
    Two orthogonally polarized optical beams in a family of Kerr-law nonlinear shifted parabolic graded-index rod lenses (1996)
    Springer
    Applied physics 63 (1996), S. 161-166 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.20 ; 42.30 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The field, the propagation and the imaging characteristics of two Gaussian optical beams with orthogonal polarization passing through a family of Kerr-law nonlinear shifted parabolic graded-index rod lenses are investigated. The coupled differential equations of the dimensionless beam-width parameters of two Gaussian optical beams are derived by using a variational approach and then solved. It is concluded that there are two regimes of propagation and that the power, the incident waist radius and the position of one beam have large effects on the field, the propagation and the imaging characteristics of the other beam.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01095268
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  • 47
    Digitale Medien
    Digitale Medien
    Second-harmonic generation with traveling-wave pulses (1996)
    Springer
    Applied physics 63 (1996), S. 237-242 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.65 ; 42.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We experimentally studied properties of traveling-wave excitation and traveling-wave pulse compression for a Nd : glass laser system with a streak camera. These properties were extended to second-harmonic generation with a type-11 KDP crystal. We found that the second-harmonic pulse generated from the chirped-fundamental pulse also has a good chirp linearity, but the spectral bandwidth and temporal duration were reduced. We demonstrated the effective subpulse suppression in the compressed pulse with the second-harmonic generation. The pulse with tilted wave front, short wavelength and high contrast ratio can be obtained by the second-harmonic generation of traveling-wave pulse.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01833792
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  • 48
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    Digitale Medien
    Self-induced transparency and self-induced darkening with a nonlinear frequency-doubling polarization interferometer (1996)
    Springer
    Applied physics 63 (1996), S. 371-374 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is shown that the system polarizer-frequency-doubling crystal(s)-analyzer has a nonlinear transmission for the fundamental wave. The intensity-dependent transmission of this device is due to the nonlinear phase shift that the fundamental beam obtains in the nonlinear crystal as a result of cascaded second-order processes. Depending on the mutual orientation of the polarizer and the analyzer such effects as self-induced transparency and self-induced darkening can be realized.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01828740
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  • 49
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    Digitale Medien
    Vector phase conjugation in Cr4+:YAG by four-wave mixing with linearly-polarized pump beams (1996)
    Springer
    Applied physics 63 (1996), S. 537-540 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We experimentally demonstrate vector phase conjugation in Cr4+:YAG saturable absorber at 1.06μm with nanosecond pulses using degenerate four-wave mixing with linearly-polarized pump beams of arbitrary strengths. The experimental results show that the phase conjugate wave produced by this method can correct depolarisation induced by a birefringent medium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01828953
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  • 50
    Digitale Medien
    Digitale Medien
    Holographic scattering lines observed with photorefractive BaTiO3 (1996)
    Springer
    Applied physics 63 (1996), S. 599-604 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.40 ; 42.65 ; 42.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We investigate holographic scattering processes in BaTiO3 pumped by two coherent copropagating waves. Four lines are observed on a screen behind the sample. The experimental results are well described by a model taking into account parametric mixing of four copropagating waves and limitations of optically induced space charge fields because of the finite trap density.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01830999
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  • 51
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    Digitale Medien
    The Ising Model with Boundaries: Integrability and Functional Relations (1998)
    Springer
    Letters in mathematical physics 46 (1998), S. 207-218 
    Details
    ISSN: 1573-0530
    Schlagwort(e): Ising model ; boundary conditions ; Boltzmann weights.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: Abstract In this Letter, we analyse the boundary conditions of the planar Ising model and determine the boundary Boltzmann weights in terms of bulk Boltzmann weights. The commutativity of the transfer matrices and their functional relations are shown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007523720496
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  • 52
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    Digitale Medien
    On the extremality of the disordered state for the Ising model on the Bethe lattice (1996)
    Springer
    Letters in mathematical physics 37 (1996), S. 137-143 
    Details
    ISSN: 1573-0530
    Schlagwort(e): 82B20 ; 82B26 ; 82B43 ; Bethe lattice ; FK representation ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: Abstract We give a simple proof that the limit Ising Gibbs measure with free boundary conditions on the Bethe lattice with the forward branching ratio k≥2 is extremal if and only if β is less or equal to the spin glass transition value, given by tanh(β c SG = 1/√k.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00416016
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  • 53
    Digitale Medien
    Digitale Medien
    Temperature and Pressure Dependencies of Thermal Transport Properties of Rocks: Implications for Uncertainties in Thermal Lithosphere Models and new Laboratory Measurements of High-Grade Rocks in the Central Fennoscandian Shield (1999)
    Springer
    Surveys in geophysics 20 (1999), S. 33-59 
    Details
    ISSN: 1573-0956
    Schlagwort(e): (AGI) ; heat flow ; lithosphere ; thermal conductivity ; thermal diffusivity ; models ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Measurements on thermal conductivity and diffusivity as functions of temperature (up to 1150 K) and pressure (up to 1000 MPa) are presented for Archaean and Proterozoic mafic high-grade rocks metamorphosed in middle and lower crustal pressures, and situated in eastern Finland, central Fennoscandian Shield. Decrease of 12–20% in conductivity and 40–55% in diffusivity was recorded between room temperature and 1150 K, which can be considered as typical of phonon conductivity. Radiative heat transfer effects were not detected in these samples. Pressure dependencies of the samples are weak if compared to crystalline rocks in general, but relatively typical for mafic rocks. The temperature and pressure dependencies of thermal transport properties (data from literature and the present study) were applied in an uncertainty analysis of lithospheric conductive thermal modellings with random (Monte Carlo) simulations using a 4-layer model representative of shield lithosphere. Model parameters were varied according to predetermined probability functions and standard deviations were calculated for lithospheric temperature and heat flow density after 1500 independent simulations. The results suggest that the variations (uncertainties) in calculated temperature and heat flow density values due to variations in the temperature and pressure dependencies of conductivity are minor in comparison to the effects produced by typical variations in the room temperature value of conductivity, heat production rate or lower boundary condition values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006655023894
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  • 54
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    Digitale Medien
    Thermal Transport in BPSCCO System Between 20 and 170 K (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 617-621 
    Details
    ISSN: 1572-9605
    Schlagwort(e): thermal conductivity ; (Bi,Pb) 2223 pellet ; thermal conductivity peak ; phonon + electron approach
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract Thermal conductivity of superconducting (Bi,Pb)2223 pellet in the temperature range 20–170 K is reported. Electronic contribution to thermal conductivity in the normal state is estimated to be ∼25%. Considering both phonon and phonon + electron approach, we attempted to examine the observed nature of the temperature dependence of thermal conductivity. Our analysis strongly supports the role of phonons as well as electrons in the origin of the thermal conductivity peak in the superconducting state. Some of the microscopic quantities evaluated from the best-fit parameters obtained from phonon + electron approach give reasonable values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007837220525
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  • 55
    Digitale Medien
    Digitale Medien
    Partition function zeros for aperiodic systems (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 285-297 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; Lee-Yang zeros ; edge singularities ; nonperiodic systems ; phase transitions ; gap labeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The study of zeros of partition functions, initiated by Yang and Lee, provides an important qualitative and quantitative tool in the study of critical phenomena. This has frequently been used for periodic as well as hierarchical lattices. Here, we consider magnetic field and temperature zeros of Ising model partition functions on several aperiodic structures. In 1D, we analyze aperiodic chains obtained from substitution rules, the most prominent example being the Fibonacci chain. In 2D, we focus on the tenfold symmetric triangular tiling which allows efficient numerical treatment by means of corner transfer matrices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183349
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  • 56
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    Digitale Medien
    Some numerical results on the block spin transformation for the 2D Ising model at the critical point (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 731-757 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; renormalization group ; finite-size conditions ; critical point
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the block spin transformation for the 2D Ising model at the critical temperatureT c . We consider the model with the constraint that the total spin in each block is zero. An old argument by Cassandro and Gallavotti strongly supports the Gibbsianness of the transformed measure, provided that such model has a critical temperatureT′ c lower thanT c . After describing a possible rigorous approach to the problem, we present numerical evidence that indeedT′ c 〈T c and study the Dobrushin-Shlosman uniqueness condition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183686
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  • 57
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    Digitale Medien
    Comparison and disjoint-occurrence inequalities for random-cluster models (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 1311-1324 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Random-cluster model ; Ising model ; Potts model ; comparison inequality ; BK inequality ; FKG inequality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A principal technique for studying percolation, (ferromagnetic) Ising, Potts, and random-cluster models is the FKG inequality, which implies certain stochastic comparison inequalities for the associated probability measures. The first result of this paper is a new comparison inequality, proved using an argument developed elsewhere in order to obtain strict inequalities for critical values. As an application of this inequality, we prove that the critical pointp c (q) of the random-cluster model with cluster-weighting factorq (≥1) is strictly monotone inq. Our second result is a “BK inequality” for the disjoint occurrence of increasing events, in a weaker form than that available in percolation theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02180133
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  • 58
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    Digitale Medien
    Corrections to the critical temperature in 2D Ising systems with Kac potentials (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 1131-1138 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Kac potential ; Ising model ; critical fluctuations ; Euclidean field theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider ad=2 Ising system with a Kac potential whose mean-field critical temperature is 1. Calling γ〉0 the Kac parameter, we prove that there existsc *〉0 so that the true inverse critical temperature βcr(γ) 〉 1 +by 2 log γ-1, for anyb〈c * and γ correspondingly small. We also show that if γ→0 andb→c *, suitably, then the correlation functions (normalized and rescaled) converge to those of a non-Gaussian Euclidean field theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183705
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  • 59
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    Digitale Medien
    The computational complexity of generating random fractals (1996)
    Springer
    Journal of statistical physics 82 (1996), S. 1299-1326 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Cluster algorithms ; computational complexity ; diffusion-limited aggregation ; Ising model ; Metropolis algorithm ; P-completeness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We examine a number of models that generate random fractals. The models are studied using the tools of computational complexity theory from the perspective of parallel computation. Diffusion-limited aggregation and several widely used algorithms for equilibrating the Ising model are shown to be highly sequential; it is unlikely they can be simulated efficiently in parallel. This is in contrast to Mandelbrot percolation, which can be simulated in constant parallel time. Our research helps shed light on the intrinsic complexity of these models relative to each other and to different growth processes that have been recently studied using complexity theory. In addition, the results may serve as a guide to simulation physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183384
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  • 60
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    Digitale Medien
    Two-dimensional gas of disks: Thermal conductivity (1996)
    Springer
    Journal of statistical physics 82 (1996), S. 1453-1466 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Kinetic theory ; thermal conductivity ; molecular dynamics ; hard disks ; Enskog's Theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The phenomenon of heat conduction in a two-dimensional gas ofN hard disks is studied in the hydrostatic regime by means of nonequilibrium molecular dynamics (N ranging from 100 to 8000). For systems withN≥1500 the temperature and density profiles observed are in excellent agreement with the continuous theory, but the conductivityk differs from the one derived from Enskog's theory in a systematic way. This difference seems to slowly decrease with increasing density.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183391
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  • 61
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    Digitale Medien
    Dynamic critical behavior of a Swendsen-Wang-Type algorithm for the Ashkin-Teller model (1996)
    Springer
    Journal of statistical physics 85 (1996), S. 297-361 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ashkin-Teller model ; Ising model ; Potts model ; Monte Carlo ; dynamical critical behavior ; cluster algorithm ; Swedsen-Wang algorithm ; Li-Sokal bound ; critical slowing down ; autocorrelation time, fitting correlated data
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the dynamic critical behavior of a Swendsen-Wang-type algorithm for the Ashkin-Teller model. We find that the Li-Sokal bound on the autocorrelation time (τint.δ≥ const xC H ) holds along the self-dual curve of the symmetric Ashkin-Teller model, and is almost, but not quite sharp. The ratio τint.δ/C H appears to tend to infinity either as a logarithm or as a small power (0.05≲p≲0.12). In an appendix we discuss the problem of extracting estimates of the exponential autocorrelation time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02174209
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  • 62
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    Digitale Medien
    Absence of renormalization group pathologies near the critical temperature. Two examples (1996)
    Springer
    Journal of statistical physics 85 (1996), S. 607-637 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; renormalization group pathologies ; Dobrushin uniqueness theorem ; completely analytic potentials
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider real-space renormalization group transformations for Ising-type systems which are formally defined by $$\exp \left[ { - H'(\sigma ')} \right] = \sum\limits_\sigma {T(\sigma ,\sigma ')} \exp \left[ { - H(\sigma )} \right]$$ whereT(σ, σ′) is a probability kernel, i.e., ∑σ′ T(σ,σ′) = 1 for every configuration σ. For each choice of the block spin configuration σ′, let σ′, let μσ′ be the measure on spin configurations σ which is formally given by taking the probability of σ to be proportional toT(σ, σ′) exp[−H(σ)]. We give a condition which is sufficient to imply that the renormalized HamiltonianH′ is defined. Roughly speaking, the condition is that the collection of measures μσ′ is in the high-temperature phase uniformly in the block spin configuration σ′. The proof of this result uses methods of Olivieri and Picco. We use our theorem to prove that the first iteration of the renormalization group transformation is defined in the following two examples: decimation with spacingb = 2 on the square lattice with β 〈 1.36β c and the Kadanoff transformation with parameterp on the trian gular lattice in a subset of the β,p plane that includes values of β greater than β c .
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02199358
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  • 63
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    Digitale Medien
    Almost sure quasilocality fails for the random-cluster model on a tree (1996)
    Springer
    Journal of statistical physics 84 (1996), S. 1351-1361 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Random-cluster model ; quasilocality ; almost sure quasilocality ; tree ; Gibbs measure ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the random-cluster model on a homogeneous tree, and show that the following three conditions are equivalent for a random-cluster measure: quasilocality, almost sure quasilocality, and the almost sure nonexistence of infinite clusters. As a consequence of this, we find that the plus measure for the Ising model on a tree at sufficiently low temperatures can be mapped, via a local stochastic transformation, into a measure which fails to be almost surely quasilocal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02174134
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  • 64
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    Digitale Medien
    Ernst Ising—Physicist and Teacher (1997)
    Springer
    Journal of statistical physics 88 (1997), S. 991-995 
    Details
    ISSN: 1572-9613
    Schlagwort(e): History of statistical physics ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The Ising model is one of the standard models in statistical physics. Since 1969 more than 13800 publications using this model have appeared. In 1997 Ernst Ising celebrated his 97th birthday. Some biographical notes and milestones of the development of the Ising model are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/B:JOSS.0000015184.19421.03
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  • 65
    Digitale Medien
    Digitale Medien
    Majority-Vote Cellular Automata, Ising Dynamics, and P-Completeness (1997)
    Springer
    Journal of statistical physics 88 (1997), S. 795-805 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Cellular automata ; Ising model ; voting models ; single sin-flip dynamics ; computational complexity ; parallel computation ; P-completeness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study cellular automata where the state at each site is decided by a majority vote of the sites in its neighborhood. These are equivalent, for a restricted set of initial conditions, to nonzero probability transitions in single spin-flip dynamics of the Ising model at zero temperature. We show that in three or more dimensions these systems can simulate Boolean circuits of AND and OR gates, and are therefore P-complete. That is, predicting their state t time-steps in the future is at least as hard as any other problem that takes polynomial time on a serial computer. Therefore, unless a widely believed conjecture in computer science is false, it is impossible even with parallel computation to predict majority-vote cellular automata, or zero-temperature single spin-flip Ising dynamics, qualitatively faster than by explicit simulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/B:JOSS.0000015172.31951.7b
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  • 66
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    Digitale Medien
    Finite-Volume Glauber Dynamics in a Small Magnetic Field (1998)
    Springer
    Journal of statistical physics 90 (1998), S. 1015-1035 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; mixing conditions ; Basuev region ; boundary conditions ; Glauber dynamics ; exponential relaxation ; spectral gap
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider Glauber dynamics on a finite cube in d-dimensional lattice (d≥2), which is associated with basic Ising model at temperature T=1/β≪1 under a magnetic field h 〉 0. We prove that if the “effective magnetic field” is positive, then the relaxation of the Glauber dynamics in the uniform norm is exponentially fast, uniformly over the size of underlying cube. The result covers the case of the free-boundary condition with arbitrarily small positive magnetic field. This paper is a continuation of an attempt initiated earlier by Schonmann and Yoshida to shed more light on the relaxation of the finite-volume Glauber dynamics when the thermodynamic parameter (β, h) is so near the phase transition line, (β, h); β c 〈 β&h = 0, that the Dobrushin–Shlosman mixing condition is no longer available.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023249608957
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  • 67
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    Digitale Medien
    Cassie's Law and Concavity of Wall Tension with Respect to Disorder (2000)
    Springer
    Journal of statistical physics 98 (2000), S. 1115-1134 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; correlation inequalities ; surface tension ; disorder
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract For the semiinfinite Ising model with quenched boundary disorder, we prove concavity inequalities for the difference of wall tensions associated with the minus and plus phases. These inequalities generalize phenomenological equalitiesknown as Cassie's law.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018663611669
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  • 68
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    Digitale Medien
    Pattern recognition and statistical mechanics (1969)
    Springer
    Journal of statistical physics 1 (1969), S. 71-88 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Decision theory ; Ising model ; Least square estimation ; Pattern recognition ; Plasmas ; Statistical mechanics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A mathematical connection is established between classes of problems in pattern recognition and in statistical mechanics. More explicitly, the former class embraces problems arising from the decision-theoretic approach to the automatic recognition of certain properties of patterns containing many targets. The latter class contains almost all problems involving the statistical mechanics of classical systems of interacting particles. The usefulness of the mathematical connection lies in the fact that it provides a bridge for the transfer of approximation methodologies from one area to the other. As examples of such a transfer this paper presents applications of a least mean square approximation method, which is well known in pattern recognition, to two problems in classical statistical mechanics, namely, the one-dimensional Ising problem and the one-component plasma problem. These problems were chosen because their solutions are well understood (the exact solution of the one-dimensional Ising model and the solution of the one-component plasma that is exact in the low concentration limit are both very well known) and consequently they are appropriate as “test beds” for the new approximation method. The simplest nontrivial approximate trial functions were used for the calculation of the average values of certain observables and the results were in agreement with the corresponding exact results for the Ising model in the limit of high temperature and for the one-component plasma in the limit of low concentration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01007242
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  • 69
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    Digitale Medien
    The Onsager formula, the fisher-hartwig conjecture, and their influence on research into Toeplitz operators (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 575-584 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; correlation functions ; spontaneous magnetization ; Toeplitz determinants ; Szegö limit theorems ; Toeplitz operators
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This is not primarily a paper about applications of mathematics to statistical physics, but rather a report on how a particular problem of statistical physics has resulted in an extensive mathematical theory. The problem alluded to is the computation of the spontaneous magnetizationM o (T) of the two-dimensional Ising model with nearest-neighbor interactions, whose solution for temperaturesT below the Curie pointT c was given by the famous formula of Lars Onsager in 1948. The theory grown out of this formula is the edifice of Toeplitz determinants, matrices, and operators.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183366
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  • 70
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    Digitale Medien
    Relaxation times in a finite Ising system with random impurities (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 893-916 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Dynamic critical phenomena ; disordered spin systems ; Ising model ; finite size ; scaling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Finite-size scaling effects of the Ising model with quenched random impurities are studied, focusing on critical dynamics. In contrast to the pure Ising model, disordered systems are characterized by continuous relaxation time spectra. Dynamic field theory is applied to compute the spectral densities of the magnetizationM(t) and ofM 2(t). In addition, universal cumulant ratios are calculated to second order in ε1/4, where ε=4−d andd〈4 denotes the spatial dimension.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183693
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  • 71
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    Digitale Medien
    Instability of renormalization-group pathologies under decimation (1995)
    Springer
    Journal of statistical physics 79 (1995), S. 25-42 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Renormalization group ; decimation ; non-Gibbsianness ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We investigate the stability and instability of pathologies of renormalization group transformations for lattice spin systems under decimation. In particular we show that, even if the original renormalization group transformation gives rise to a non-Gibbsian measure, Gibbsianness may be restored by applying an extra decimation transformation. This fact is illustrated in detail for the block spin transformation applied to the Ising model. We also discuss the case of another non-Gibbsian measure with nicely decaying correlations functions which remains non-Gibbsian after arbitrary decimation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02179382
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  • 72
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    Digitale Medien
    sl(N) Onsager's algebra and integrability (1996)
    Springer
    Journal of statistical physics 82 (1996), S. 87-113 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Onsager's algbera ; loop algebras ; Ising model ; integrability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We define ansl(N) analog of Onsager's algebra through a finite set of relations that generalize the Dolan-Grady defining relations for the original Onsager's algebra. This infinite-dimensional Lie algebra is shown to be isomorphic to a fixed-point subalgebra ofsl(N) loop algebra with respect to a certain involution. As the consequence of the generalized Dolan-Grady relations a Hamiltonian linear in the generators ofsl(N) Onsager's algebra is shown to posses an infinite number of mutually commuting integrals of motion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02189226
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  • 73
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    Digitale Medien
    Some new results on the two-dimensional kinetic Ising model in the phase coexistence region (1996)
    Springer
    Journal of statistical physics 84 (1996), S. 655-696 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; Glauber dynamics ; relaxation time
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider a Glauber dynamics reversible with respect to the two-dimensional Ising model in a finite square of sideL with open boundary conditions, in the absence of an external field and at large inverse temperature β. We prove that the gap in the spectrum of the generator restricted to the invariant subspace of functions which are even under global spin flip is much larger than the true gap. As a consequence we are able to show that there exists a new time scalet even, much smaller than the global relaxation timet rel, such that, with large probability, any initial configuration first relaxes to one of the two “phases” in a time scale of ordert even and only after a time scale of the order oft rel does it reach the final equilibrium by jumping, via a large deviation, to the opposite phase. It also follows that, with large probability, the time spent by the system during the first jump from one phase to the opposite one is much shorter than the relaxation time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02179653
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  • 74
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    Digitale Medien
    Equivalences of the large deviation principle for Gibbs measures and critical balance in the Ising model (1997)
    Springer
    Journal of statistical physics 86 (1997), S. 149-164 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; Gibbs measures ; large-deviation principle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper we obtain the equivalence of the large deviation principle for Gibbs measures with and without an external field. For the Ising model, the equivalence allows us to study the result of competing influences of a positive external fieldh and a negative boundary condition in the cube (Λ(B/h) ash↘0 for variousB. We find a critical balance at a valueB 0 ofB.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02180201
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  • 75
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    Digitale Medien
    Metastability in the Two-Dimensional Ising Model with Free Boundary Conditions (1998)
    Springer
    Journal of statistical physics 90 (1998), S. 211-226 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; stochastic dynamics ; metastability ; nucleation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We investigate metastability in the two dimensional Ising model in a square with free boundary conditions at low temperatures. Starting with all spins down in a small positive magnetic field, we show that the exit from this metastable phase occurs via the nucleation of a critical droplet in one of the four corners of the system. We compute the lifetime of the metastable phase analytically in the limit T → 0, h → 0 and via Monte Carlo simulations at fixed values of T and h and find good agreement. This system models the effects of boundary domains in magnetic storage systems exiting from a metastable phase when a small external field is applied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023255802455
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  • 76
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    Digitale Medien
    Improved Peierls Argument for High-Dimensional Ising Models (1998)
    Springer
    Journal of statistical physics 90 (1998), S. 1051-1059 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; Peierls contour ; low-temperature expansion ; high dimension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the low-temperature expansion for the Ising model on $$\mathbb{Z}^d ,d \geqslant 2$$ , with ferromagnetic nearest neighbor interactions in terms of Peierls contours. We prove that the expansion converges for all temperatures smaller than Cd(log d)−1, which is the correct order in d.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023205826704
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  • 77
    Digitale Medien
    Digitale Medien
    The O(n) Loop Model on the 3–12 Lattice (1998)
    Springer
    Journal of statistical physics 92 (1998), S. 1203-1208 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Loop model ; criticality ; universality ; 3–12 lattice ; self-avoiding walk ; connective constant ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The partition function of the O(n) loop model on the honeycomb lattice is mapped to that of the O(n) loop model on the 3–12 lattice. Both models share the same operator content and thus critical exponents. The critical points are related via a simple transformation of variables. When n = 0 this gives the recently found exact value μ = 1.711041... for the connective constant of self-avoiding walks on the 3–12 lattice. The exact critical points are recovered for the Ising model on the 3–12 lattice and the dual asanoha lattice at n = 1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023065215233
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  • 78
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    Digitale Medien
    On the Phase Diagram of the Random Field Ising Model on the Bethe Lattice (1998)
    Springer
    Journal of statistical physics 93 (1998), S. 33-78 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Random external field ; Ising model ; Gibbs states ; ground states ; Bethe lattice ; residual entropy ; dipole configurations ; Griffiths singularities
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The ferromagnetic Ising model on the Bethe lattice of degree k is considered in the presence of a dichotomous external random field ξ x = ±α and the temperature T≥0. We give a description of a part of the phase diagram of this model in the T−α plane, where we are able to construct limiting Gibbs states and ground states. By comparison with the model with a constant external field we show that for all realizations ξ = {ξ x = ±α} of the external random field: (i) the Gibbs state is unique for T 〉 T c (k ≥ 2 and any α) or for α 〉 3 (k = 2 and any T); (ii) the ±-phases coexist in the domain {T 〈 T c, α ≤ H F(T)}, where T c is the critical temperature and H F(T) is the critical external field in the ferromagnetic Ising model on the Bethe lattice with a constant external field. Then we prove that for almost all ξ: (iii) the ±-phases coexist in a larger domain {T 〈 T c, α ≤H F(T) + ε(T)}, where ε(T)〉0; and (iv) the Gibbs state is unique for 3≥α≥2 at any T. We show that the residual entropy at T = 0 is positive for 3≥α≥2, and we give a constructive description of ground states, by so-called dipole configurations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/B:JOSS.0000026727.43077.49
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  • 79
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    Digitale Medien
    An Equilibrium Lattice Model of Wetting on Rough Substrates (1999)
    Springer
    Journal of statistical physics 94 (1999), S. 299-320 
    Details
    ISSN: 1572-9613
    Schlagwort(e): wetting ; surface tension ; rough surfaces ; Wenzel's law ; semi-infinite systems ; Ising model ; cluster expansions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider a semi-infinite 3-dimensional Ising system with a rough wall to describe the effect of the roughness r of the substrate on wetting. We show that the difference of wall free energies Δτ(r)=τ AW(r)−τ BW(r) of the two phases behaves like Δτ(r)∼rΔτ(1), where r=1 characterizes a purely flat surface, confirming at low enough temperature and small roughness the validity of Wenzel's law, cos θ(r)≈r cos θ(1), which relates the contact angle θ of a sessile droplet to the roughness of the substrate
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004531917428
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  • 80
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    Digitale Medien
    The Ising Model on a Quenched Ensemble of c=−5 Gravity Graphs (1999)
    Springer
    Journal of statistical physics 94 (1999), S. 321-345 
    Details
    ISSN: 1572-9613
    Schlagwort(e): dynamical triangulations ; quenched disorder ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study with Monte Carlo methods an ensemble of c=−5 gravity graphs, generated by coupling a conformal field theory with central charge c=−5 to two-dimensional quantum gravity. We measure the fractal properties of the ensemble, such as the string susceptibility exponent γ s and the intrinsic fractal dimension d H. We find γ s=−1.5(1) and d H=3.36(4), in reasonable agreement with theoretical predictions. In addition, we study the critical behavior of an Ising model on a quenched ensemble of the c=−5 graphs and show that it agrees, within numerical accuracy, with theoretical predictions for the critical behavior of an Ising model coupled dynamically to two-dimensional quantum gravity, with a total central charge of the matter sector c=−5.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004583901498
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  • 81
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    Digitale Medien
    Statistical Entropy of a Lattice-Gas Model: Multiparticle Correlation Expansion (1999)
    Springer
    Journal of statistical physics 96 (1999), S. 135-167 
    Details
    ISSN: 1572-9613
    Schlagwort(e): statistical entropy ; multiparticle correlations ; cumulant expansion ; lattice gases ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A formula expressing the statistical entropy of a lattice-gas model as a multiparticle correlation expansion is derived in the grand-canonical and in the canonical ensembles. The differences from the analogous expansion in the continuum case are elucidated. The Ising model in one dimension is discussed as a case study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004520432275
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  • 82
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    Digitale Medien
    Renormalization-Group Transformations Under Strong Mixing Conditions: Gibbsianness and Convergence of Renormalized Interactions (1999)
    Springer
    Journal of statistical physics 97 (1999), S. 831-915 
    Details
    ISSN: 1572-9613
    Schlagwort(e): renormalization group ; Gibbsianness ; finite-size conditions ; complete analyticity ; strong mixing ; equivalence of ensembles ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper we study a renormalization-group map: the block averaging transformation applied to Gibbs measures relative to a class of finite-range lattice gases, when suitable strong mixing conditions are satisfied. Using a block decimation procedure, cluster expansion, and detailed comparison between statistical ensembles, we are able to prove Gibbsianness and convergence to a trivial (i.e., Gaussian and product) fixed point. Our results apply to the 2D standard Ising model at any temperature above the critical one and arbitrary magnetic field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004620929047
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  • 83
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    Digitale Medien
    Universality and Conformal Invariance for the Ising Model in Domains with Boundary (2000)
    Springer
    Journal of statistical physics 98 (2000), S. 131-244 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; boundary conditions ; renormalization group ; free boson ; conformal invariance ; critical phenomena
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The partition function with boundary conditions for various two-dimensional Ising models is examined and previously unobserved properties of nonformal invariance and universality are established numerically.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018674822185
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  • 84
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    Digitale Medien
    Monte Carlo Transition Dynamics and Variance Reduction (2000)
    Springer
    Journal of statistical physics 98 (2000), S. 321-345 
    Details
    ISSN: 1572-9613
    Schlagwort(e): statistical mechanics ; variance reduction ; Monte Carlo algorithms ; Metropolis algorithm ; statistical estimators ; Ising model ; histogram methods ; transition probabilities
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract For Metropolis Monte Carlo simulations in statistical physics, efficient, easy- to-implement, and unbiased statistical estimators of thermodynamic properties are based on the transition dynamics. Using an Ising model example, we demonstrate (problem-specific) variance reductions compared to conventional histogram estimators. A proof of variance reduction in a microstate limit is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018635108073
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  • 85
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    Digitale Medien
    A Comparison Between Broad Histogram and Multicanonical Methods (2000)
    Springer
    Journal of statistical physics 99 (2000), S. 691-705 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Monte Carlo methods ; Ising model ; computational physics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We discuss the conceptual differences between the broad histogram (BHM) and reweighting methods in general, and particularly the so-called multicanonical (MUCA) approaches. The main difference is that BHM is based on microcanonical, fixed-energy averages which depend only on the good statistics taken inside each energy level. The detailed distribution of visits among different energy levels, determined by the particular dynamic rule one adopts, is irrelevant. Contrary to MUCA, where the results are extracted from the dynamic rule itself, within BHM any microcanonical dynamics could be adopted. As a numerical test, we have used both BHM and MUCA in order to obtain the spectral energy degeneracy of the Ising model in 4×4×4 and 32×32 lattices, for which exact results are known. We discuss why BHM gives more accurate results than MUCA, even using the same Markovian sequence of states. In addition, such an advantage increases for larger systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018679025763
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  • 86
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    Digitale Medien
    Investigation of two-wave mixing in arbitrary oriented sillenite crystals (1996)
    Springer
    Applied physics 64 (1996), S. 49-56 
    Details
    ISSN: 0340-3793
    Schlagwort(e): PACS: 42.40 ; 42.65 ; 42.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract.  A generalized systematic description of the Two-Wave Mixing (TWM) process in sillenite crystals allowing for arbitrary orientation of the grating vector is presented. An analytical expression for the TWM gain is obtained for the special case of plane waves in a thin crystal (∣g∣d≪1) with large optical activity (∣g∣/ϱ≪1, g is the coupling constant, ϱ the rotatory power, d the crystal thickness). Using a two-dimensional formulation the scope of the nonlinear equations describing TWM can be extended to finite beams in arbitrary geometries and to any crystal parameters. Two promising applications of this formulation are proposed. The polarization dependence of the TWM gain is used for the flattening of Gaussian beam profiles without expanding them. The dependence of the TWM gain on the interaction length is used for the determination of the crystal orientation. Experiments carried out on Bi12GeO20 crystals of a non-standard cut are in good agreement with the results of modelling.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003400050144
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  • 87
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    Digitale Medien
    Optical second-harmonic generation by supported metal clusters: Size and shape effects (1995)
    Springer
    Applied physics 60 (1995), S. 607-612 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.65 ; 68.55 ; 36.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Optical Second Harmonic Generation (SHG) by metal clusters has been investigated. For this purpose clusters were generated by the deposition and nucleation of metal atoms on a LiF(100) single crystal surface under ultrahigh vacuum conditions. The size and shape of the metal particles was characterized by optical transmission spectroscopy. The SHG intensity was detected in situ as a function of cluster size during the nucleation. Fundamental wavelengths of λ=1064 and 532 nm were used and the SHG signal was measured for different polarization combinations of the incident and registered light. SH radiation is detectable for particles as small as approximately 1 nm. The signal grows monotonically as a function of particle size, passes a maximum and finally drops off. This behavior is discussed in terms of resonant enhancement of the signal by surface plasmon excitation and changes ofχ (2) as a function of particle size and shape. In further experiments the chemisorption of oxygen on the surface of the metal particles was studied. The SH signal decreases as a function of oxygen coverage and amounts to only about 15% of the initial value upon chemisorption of one monolayer. This indicates that the SH signal originates almost exclusively from the surface of the clean clusters and that higher order bulk contributions are negligible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538536
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  • 88
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    Digitale Medien
    Calorimetric measurement of two-photon absorption and color-center formation in ultraviolet-window materials (1996)
    Springer
    Applied physics 62 (1996), S. 143-149 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 61.80 ; 42.70 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Intensity-dependent absorption of 25 ns excimer laser pulses in common UV-window materials was investigated. By employing a calorimetric technique which provides greatly enhanced sensitivity compared to transmissive measurements, two-photon absorption coefficients were determined at intensities of 2–80 MW/cm2 and found to be in good agreement with previous measurements at 10–100 GW/cm2. Also, color-center formation in fused silica was observed. It was possible to quantify transient and cumulative effects as a function of intensity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01575711
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  • 89
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    Digitale Medien
    Adsorption of oxygen and hydrogen on Pt(111) studied with second-harmonic generation (1995)
    Springer
    Applied physics 60 (1995), S. 209-215 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 68.35 ; 82.20 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The adsorption of oxygen and hydrogen on a Pt(111) surface has been studied with phase-sensitive Second-Harmonic Generation (SHG) signal detection. The SHG-signal change measured with p-in, p-out polarization during the adsorption of oxygen and hydrogen was found to be different in amplitude and phase for the two adsorbates. At the wavelength used (1064 nm), only a localized interaction between adsorbate and substrate is seen, leading to a linear dependence of the susceptibility on the coverage. Sticking coefficients,sθ, and their coverage dependence were determined. For hydrogen, a linear decrease insθ with coverage was found; the initial sticking coefficient beings 0=0.06 at a temperature ofT=130 K. For oxygen,sθ whows a quadratic decrease with coverage, strongly dependent on temperature, withs 0=0.05 atT=350 K. A method based on these results is proposed, which would allow the determination of adsorbate coverages of coadsorption systems with SHG using phase-sensitive signal detection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538248
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  • 90
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    Digitale Medien
    Second-order nonlinear susceptibilities of surfaces (1995)
    Springer
    Applied physics 60 (1995), S. 1-12 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 73.60 ; 82.65 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Systematic studies were carried out with the goal to further develop optical Second-Harmonic Generation (SHG) as a tool for surface and interface analysis. For this purpose hexadecane thiol, HS(CH2)15CH3, on polycrystalline Au films served as a model system to study the spectral behavior of the susceptibility of the gold surface and its variation as a function of coverage. Experiments have been performed at different coverages, with different polarization combinations of the incident and detected light, different angles of incidence and different wavelengths ranging from z=615 nm to 660 nm. In addition to the intensity of the generated second-harmonic light, its phase was measured. As a result, a complete determination of all independent elements of the susceptibility tensor became possible. The studies with different excitation wavelengths reveal the presence of resonances of the tensor elements and strikingly demonstrate the importance of phase measurements for an unambiguous interpretation of the data. The superposition of resonant contributions originating from different elements of the susceptibility tensor is discussed and gives rise to very distinct and peculiar spectral features.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01577605
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  • 91
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    Digitale Medien
    Particularities of Heat Conduction in Nanostructures (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 199-204 
    Details
    ISSN: 1572-896X
    Schlagwort(e): nanoscale heat transfer ; nanoparticles ; nanowires ; phonons ; superlattices ; thermal conductivity ; thin films ; microscale effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik , Technik allgemein
    Notizen: Abstract Heat conduction in nanostructures differs significantly from that in macrostructures because the characteristic length scales associated with heat carriers, i.e., the mean free path and the wavelength, are comparable to the characteristic length of nanostructures. In this communication, particularities associated with phonon heat conduction in nanostructures, the applicability of the Fourier law, and the implications of nanoscale heat transfer effects on nanotechnology are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010003718481
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  • 92
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    Digitale Medien
    Investigation on the effective conductivities of carbon/carbon fiber composites with inhomogeneous interphase (1997)
    Springer
    Applied mathematics and mechanics 18 (1997), S. 211-220 
    Details
    ISSN: 1573-2754
    Schlagwort(e): composite ; thermal conductivity ; inhomogeneous interphase ; Mori-Tanaka method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract Thermal conductivities of carbon/carbon fiber composites with inhomogeneous interphase are studied in thtis paper. The inhomogeneous interphase is modeled approximately as a multilayered structure consisting of many thin layers having homogeneous properties, and close-formed solution of the effective conductivities of the composites is obtained by using the Mori-Tanaka mean-field concept.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02453363
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  • 93
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    Digitale Medien
    Nonisothermal polymeric fluids (1996)
    Springer
    Rheologica acta 35 (1996), S. 103-109 
    Details
    ISSN: 1435-1528
    Schlagwort(e): Transport properties ; thermal conductivity ; FENE dumbbell model ; polymer solutions ; thermal diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract The phase-space kinetic theory for polymeric liquid mixtures has been further developed for molecular models without internal constraints. The theory provides expressions for the mass, momentum, and energy fluxes, each of which may in general be influenced by concentration, velocity, and temperature gradients. To illustrate the use of these results, the thermal conductivity for a dilute polymer solution is derived; the FENE dumbbell model is used to describe the mechanical behavior of the polymer chains. The Hookean dumbbell results can be obtained by letting the “finite extensibility parameter” b tend to infinity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00396036
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  • 94
    Digitale Medien
    Digitale Medien
    Probing the Upper Critical Field of κ-(BEDT-TTF)2Cu(NCS)2 (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 497-500 
    Details
    ISSN: 1572-9605
    Schlagwort(e): Organic superconductors ; Josephson plasma ; thermal conductivity ; upper critical field
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract Studies of heat conduction and microwave absorption in the vortex state of κ-(BEDT-TTF)2Cu(NCS)2 reveal some of the specific aspects of superconductivity in this system. Moreover they allow us to probe the destruction of bulk superconductivity by a magnetic field. The two set of results yield identical magnitudes for the upper critical field with a temperature dependence distinctly different from the one suggested by the onset of resistive transition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007771815553
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  • 95
    Digitale Medien
    Digitale Medien
    Heat conduction in Ba1−xKxBiO3 (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 445-448 
    Details
    ISSN: 1572-9605
    Schlagwort(e): High-T c superconductors ; thermal conductivity ; magnetization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We have investigated heat conduction of single crystal Ba1−xKxBiO3 in the temperature range of 2–300 K and in a magnetic field of up to 6 Tesla. Temperature dependence of thermal conductivityκ(T) reveals the participation of both electrons and phonons with their relative contributions that depend critically on the potassium doping concentration. Crystals underdoped with potassium (samples with higherT c) exhibit a strong suppression ofκ and a glass-like temperature dependence. In contrast, those with a higher potassium content (lowerT c) show an increase as temperature decreases with a peak near 23 K. Field dependence ofκ(H) is also very sensitive to the level of potassium doping. Crystals exhibiting a large phonon contribution show an initial drop inκ(H) at low fields followed by a minimum and then a slow rise to saturation as the field increases. The initial drop is due to the additional phonon scattering by magnetic vortices as the sample enters a mixed state. The high field behavior ofκ(H), arising from a continuous break-up of Cooper pairs, exhibits scaling which suggests the presence of an unconventional superconducting gap structure in this material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00722826
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  • 96
    Digitale Medien
    Digitale Medien
    The field dependence of the thermal conductivity: Evidence for nodes in the gap (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 449-452 
    Details
    ISSN: 1572-9605
    Schlagwort(e): thermal conductivity ; Andreev reflection ; vortex lines ; mixed phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The increased thermal conductivity below Tc in YBa2Cu3O7−x (YBCO) is shown to agree with the microwave electrical conductivity, affirming that increase is due to quasiparticle conduction The field dependence, particularly in the conducting plane permits us to separate phonon and quasiparticle contributions for both YBCO and Tℓ2Ba2CuO6 single crystals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00722827
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  • 97
    Digitale Medien
    Digitale Medien
    Solvable models in statistical mechanics, from Onsager onward (1995)
    Springer
    Journal of statistical physics 78 (1995), S. 7-16 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Statistical mechanics ; lattice models ; Ising model ; solvable models ; integrable systems ; Yang-Baxter relations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract There is now a whole field in mathematical physics concerned with solvable models in statistical mechanics, field theory, and related areas. We indicate the influence that Onsager's solution of the planar Ising model has had, and continues to have, on this field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183337
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  • 98
    Digitale Medien
    Digitale Medien
    Ising metamagnet under staggered field (1995)
    Springer
    Journal of statistical physics 81 (1995), S. 837-842 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; staggered field ; metastable state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report a Monte Carlo simulation of the layered Ising antiferromagnet under an external magnetic field. We show that under a staggered field, there occurs a phase transition from a metastable state which follows a Vogel-Fulcher law. For a staggered intrasublattice interaction a similar situation occurs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02179260
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  • 99
    Digitale Medien
    Digitale Medien
    Constrained variational problem with applications to the Ising model (1996)
    Springer
    Journal of statistical physics 83 (1996), S. 867-905 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Ising model ; Wulff shape ; large deviations ; boundary effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We continue our study of the behavior of the two-dimensional nearest neighbor ferromagnetic Ising model under an external magnetic fieldh, initiated in our earlier work. We strengthen further a result previously proven by Martirosyan at low enough temperature, which roughly states that for finite systems with (−)-boundary conditions under a positive external field, the boundary effect dominates in the system if the linear size of the system is of orderB/h withB small enough, while ifB is large enough, then the external field dominates in the system. In our earlier work this result was extended to every subcritical value of the temperature. Here for every subcritical value of the temperature we show the existence of a critical valueB 0 (T) which separates the two regimes specified above. We also find the asymptotic shape of the region occupied by the (+)-phase in the second regime, which turns out to be a “squeezed Wulff shape”. The main step in our study is the solution of the variational problem of finding the curve minimizing the Wulff functional, which curve is constrained to the unit square. Other tools used are the results and techniques developed to study large deviations for the block magnetization in the absence of the magnetic field, extended to all temperatures below the critical one.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02179548
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  • 100
    Digitale Medien
    Digitale Medien
    One-dimensional random-field ising model: Gibbs states and structure of ground states (1996)
    Springer
    Journal of statistical physics 84 (1996), S. 1077-1093 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Gibbs states ; ground states ; residual entropy ; random field ; Ising model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the random Gibbs field formalism for the ferromagnetic ID dichotomous random-field Ising model as the simplest example of a quenched disordered system. We prove that for nonzero temperatures the Gibb state is unique for any realization of the external field. Then we prove that asT→0, the Gibbs state converges to a limit, a ground state, for almost all realizations of the external field. The ground state turns out to be a probability measure concentrated on an infinite set of configurations, and we give a constructive description of this measure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02174129
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