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  • 42.65
  • Calcium
  • Springer  (418)
  • Cambridge University Press
  • Frontiers Media
  • 2020-2022
  • 1995-1999  (141)
  • 1980-1984  (186)
  • 1975-1979  (91)
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  • 1
    ISSN: 1436-6215
    Keywords: Strontium ; oraler Strontium-Test ; Calcium ; Absorption ; gesunde Probanden ; Strontium ; oral strontium test ; calcium ; absorption ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: Summary Intestinal strontium absorption has been discussed recently as an indirect measure for calcium uptake. Prerequisite for the clinical use of an oral strontium test is the availability of a reliable procedure including controlled strontium supply, sample pretreatment and analysis as well as the assessment of normal values. In the present study, a group of young females (n=33; 24.0 ± 2.7 y; BMI 21.5 ± 1.9) received an oral dose of 2.27 mmol strontium in a standardized breakfast that contained 0.625 mmol calcium. Before and 220 min after the bolus serum strontium concentrations were determined by means of atomic absorption spectrophotometry (coefficient of variation: within day 4.8 %, n=10; day-to-day 9.5 %, n=8). The error of the method was 2.7 %. Calculation of the fractional strontium absorption rate considered the respective distribution volume (extracellular fluid; either estimated using body weight or determined by means of bioimpedance analysis [BIA]). Average absorption rates were 13.3 ± 3.1 % and, considering BIA measurement 13.6 ± 2.6 %, respectively. Smoking, exercise and, use of oral contraceptives showed no effects. Our oral strontium test is characterized by excellent reliability, easy handling and low costs and, thus, is suitable for routine use.
    Notes: Zusammenfassung Die Erfassung der Strontiumabsorption wird heute als indirektes Verfahren zur Beurteilung der intestinalen Calciumabsorption diskutiert. Voraussetzung für die klinische Anwendung ist ein vertrauenswürdiges Testverfahren inclusive kontrollierter Strontiumgabe, Probenaufarbeitung und -analyse sowie die Erfassung von Normalwerten. Für unsere Studien wurde ein Kollektiv junger Frauen (n=33, 24,0 ± 2,7 Jahre; BMI 21,5 ± 1,9) herangezogen. Die Probandinnen erhielten eine Bolusgabe von 2,27 mmol Strontium zusammen mit einem Standardfrühstück (ca. 0,625 mmol Calcium). Vor und 220 min nach der Bolusgabe erfolgte die Bestimmung des Serum-Strontiumgehaltes mittels Atomabsorptionsspektrometrie. Der Variationskoeffizient der Methode lag innerhalb eines Tages bei 4,8 % (n=10) und von Tag zu Tag 9,5 % (n=8). Der Fehler der Methode betrug 2,7 %. Die Berechnung der fraktionellen Strontiumabsorptionsrate erfolgte unter Berücksichtigung des entsprechenden Verteilungsraumes (Extrazellulärflüssigkeit; Schätzverfahren über Körpergewicht bzw. Bioimpedanz-Analyse [BIA]). Die Strontiumabsorptionsrate lag im Mittel bei 13,3 ± 3,1 %, unter Berücksichtigung der BIA-Werte bei 13,6 ± 2,6 %. Rauchen, sportliche Aktivität bzw. Einnahme oraler Kontrazeptiva zeigten keinen Einfluß. Das hier vorgestellte Testverfahren ist aufgrund seiner hohen Vertrauenswürdigkeit und relativ einfacher Handhabung für Routine-untersuchungen geeignet.
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  • 2
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    Monatshefte für Chemie 112 (1981), S. 149-156 
    ISSN: 1434-4475
    Keywords: Calcium ; Gallium ; Oxygen ; Single Crystal ; X-Ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hitherto unknown compound Ca3Ga4O9 was prepared and investigated by X-ray single crystal methods. Ca3Ga4O9 has orthorhombic symmetry:a=1435.8;b=1682.5;c=532.1 pm; space group C 2v 11 −Cmm2,Z=6. The tetrahedra network (circles of 4 and 5 GaO4-tetrahedra) and the surrounding of Ca2+ are described and discussed with respect to other oxogallates.
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  • 3
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    Cellular and molecular life sciences 52 (1996), S. 1091-1100 
    ISSN: 1420-9071
    Keywords: Calcium ; ATPase ; calmodulin ; ion pumps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The Ca2+ pump of the plasma membrane (PMCA) is regulated by a number of agents. The most important is calmodulin (CaM), which binds to a domain located in the C-terminal portion of the pump, removing it from an autoinhibitory site next to the active site. The CaM-binding domain is preceded by an acidic sequence which contains a hidden signal for endoplasmic reticulum (ER) retention. Chimeras of the PMCA and endoplasmic reticulum (SERCA) pumps have revealed the presence of a strong signal for ER retention in the first 45 residues of the SERCA pump. Four gene products of the PMCA pump are known: two of them (1 and 4) are ubiquitously expressed, two (2 and 3) are specific for nerve cells and may be induced by their activation. Mutagenesis work has identified four residues in three of the transmembrane domains of the pump which may be components of the trans-protein Ca2+ path. The mutation of two of these residues alters the membrane targeting of the pump.
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  • 4
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    Cellular and molecular life sciences 51 (1995), S. 976-979 
    ISSN: 1420-9071
    Keywords: Calcium ; T lymphocytes ; aging ; psychosocial stress ; overcrowding ; animal housing ; lymphocyte activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Intracellular calcium concentration is a sensitive marker of the homeostasis of living cells, and its increase is an essential step of T lymphocyte activation. Changes in the environment provoke an adaptive stress-response of the organism. In our present work we have investigated the effect of chronic overcrowding on resting and lectin-stimulated cytoplasmic free calcium concentration of splenic T lymphocytes from young and aged CBA/CA mice (50 animals total). The animals were kept under ‘normal’ (68 cm2/animal) or ‘overcrowded’ (22 cm2/animal) conditions for 3 months. Young animals showed no change in resting and stimulated calcium after overcrowding. T cells from aged mice, however, displayed significantly smaller levels of both resting and lectin-stimulated intracellular calcium concentration (p〈0.01 each), as compared to those of the non-stressed, aged animals. This inadequate adaptation in the calcium metabolism of T lymphocytes may significantly contribute to the diminished immune response of the aged in stress.
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  • 5
    ISSN: 1432-1890
    Keywords: Calcium ; Iron ; Lead ; Phosphorus ; Short roots ; X-ray microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Norway spruce [Picea abies (L.) Karst.] seedlings, nonmycorrhizal of mycorrhizal with Laccaria laccata or Paxillus involutus were grown in a quartz sand-nutrient solution system for 6 months and then treated with 5 μM Pb for 4 days. Element contents of cortex cell wall of young, medium and old short roots were determined by X-ray microanalysis of longitudinal thin sections. The Pb content was influenced neither by age nor by the distance from the root tip (up to 1.7 mm) but was significantly lower in the P. involutus mycorrhizae than in the L. laccata mycorrhizae or in nonmycorrhizal short roots. In the P. involutus mycorrhizae, the P content of the cortex cell walls was twice as high in young mycorrhizae than in old mycorrhizae. In the nonmycorrhizal short roots and the L. laccata mycorrhizae, P content was influenced neither by age nor by distance from the root tip. The Ca and Fe contents of the cortex cell walls increased with age in the nonmycorrhizal short roots and the mycorrhizae. It is concluded that the element content of the cortex cell walls of short roots is strongly influenced by age, while the distance from the root tip seems to be of minor importance.
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  • 6
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    Applied physics 34 (1984), S. 123-128 
    ISSN: 1432-0649
    Keywords: 42.55R ; 42.60D ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pulse-shortening and pulse broadening effects in passively mode-locked lasers are analysed. A steady-state pulse duration limit is calculated and compared with round-trip simulations. The numerical calculations apply to a picosecond Nd: glass laser. Methods of short-pulse generation are discussed.
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  • 7
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    Applied physics 34 (1984), S. 171-173 
    ISSN: 1432-0649
    Keywords: 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Interference of resonant ninth-order and nonresonant seventh-order nonlinear polarizations in Hg atoms has been studied, and direct conversion of fundamental ir radiation into the vuv has been obtained. The interference has been observed in the form of a Fano-Boitler contour. The efficiency of generation by ninth-order processes appears to be higher than that by seventh-order.
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  • 8
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    Applied physics 35 (1984), S. 77-82 
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The coexistence of bistability and repetitive passive Q-switching of a CO2 laser with a gaseous saturable absorber has been investigated experimentally. With CH3F as the saturable absorber bistability has been observed simultaneously with passive Q-switching, whereas with CH3OH either one of these phenomena can only exist, as demonstrated for the first time. The measured features of both systems can be explained qualitatively by rate-equation theory.
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  • 9
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    Applied physics 27 (1982), S. 83-91 
    ISSN: 1432-0649
    Keywords: 42.65 ; 06 ; 35 ; 07.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The space-time properties of the correlator of the light intensities scattered from resonant atoms are studied. It is shown that in measuring such a correlator by the method of optical shifts, an appreciable contribution appears from the anomalous correlator of the scattered field amplitudes. It is simple to observe this correlator in the field of a standing wave by measuring the correlation of oppositely scattered rays. The spectral and polarization properties of such a correlator are studied. Its investigation is of interest for high-resolution spectroscopy because it allows information to be obtained on the natural width of a line in conditions of strong Doppler broadening. It is important to stress that this is possible in a linear approximation with respect to the strength of the external field in contrast to the methods of laser spectroscopy based on nonlinear effects.
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  • 10
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
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  • 11
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    Applied physics 29 (1982), S. 263-267 
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The duration, shape, and background intensity level of pulses of a passively modelocked Nd-glass laser are determined by noncollinear phase-matched four-photon frequency mixing of time-separated fundamental and second-harmonic pulses in a KI crystal. The pulse shape is found to be slightly asymmetric with slower trailing than rising parts. The background intensity level before and behind the main pulse is about 5¢10−6 the peak pulse intensity.
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  • 12
    ISSN: 1432-0649
    Keywords: 32 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stimulated Raman scattering has been experimentally studied by using the process of two-step ionization of a Na atomic beam. A dip that is due to a resonance at a combination frequency corresponding to the forbidden 3S–4S transition of a Na atom was observed in the signal of nonresonant photoionization when two laser frequencies λ1=284.5 nm and λ2=1.06 μm were overlapped.
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  • 13
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.65 ; 61.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Absorption recovery kinetics data on the picosecond time-scale of a high signalto-noise ratio can be obtained by using continuously operating synchronously modelocked dye lasers. We show that such data make it possible to determine multiple exponential decays with small differences in rate constants. We also show that an absolute prerequisite to accomplish this is that the measurements are performed at a number of different wavelengths, and that the decays are monitored in a time interval corresponding to several lifetimes. These considerations are demonstrated by measurements on two carbocyanine dyes, DQOCI and pinacyanol, respectively.
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  • 14
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    Applied physics 33 (1984), S. 225-234 
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated two-photon resonant up conversion of 375 to 159 nm coherent radiation using the four-frequency process ω159=2ω375+ω1040 in cadmium vapour, where the ir component (1040 nm) is internally generated by the 375 nm pump tuned to the Cd two-photon transition 5s 2 1 S 0→5s6s 1 S 0. Scaling laws and tuning behaviour of both the 159 and 1040 nm output power were measured up to 1×108 W cm−2 pump intensity and 2×1017 cm−3 Cd number density. The results are compared to numerical calculations based on semiclassical theory in a stationary perturbation approximation up to third order. Here, in accordance with experimental results, the ir component was assumed to originate from a superposition of stimulated emission and parametric generation. The observed saturation effects turned out to be mainly due to population changes of the atomic levels involved and are qualitatively reproduced by calculations. Discrepancies with respect to absolute output levels are discussed in terms of the approximations in the theoretical formalism.
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  • 15
    ISSN: 1432-0649
    Keywords: 35.80 ; 42.65 ; 78.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The coherent excitation of molecular vibrations in liquids via off-resonant stimulated Raman amplification is shown to consist of two parts with vastily different spectral and temporal properties. One component situated at the frequency differenceω L −eω S of the driving fields follows almost instantaneously the system response function. The second part at the eigenfrequency eω 0 carries information on the vibrational dephasing. Detecting both frequency components simultaneously by coherent anti-Stokes probe scattering a novel 2-channel method is demonstrated. The vibrational dephasing time of thev 3-mode of CH3I is directly measured to beT 2=2.6±0.15 ps. This result gives experimental support to the deconvolution techniques required in conventional spectroscopy.
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  • 16
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    Applied physics 34 (1984), S. 69-72 
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Greatly improved second-harmonic emission has been obtained from dye monolayers adsorbed at quartz etalons. Two different types of interferometers have been studied in terms of the SH signal from dye coverage versus harmonic background emission. The phasematching-like conditions for constructive interferometric enhancement and the concomitant spatial and spectral emission characteristics are discussed in detail.
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  • 17
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    Applied physics 35 (1984), S. 149-153 
    ISSN: 1432-0649
    Keywords: 42.65 ; k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The application of the resonant light pressure created by an axially symmetrical light field for collimating atomic beams has been considered. As an example, consideration is given to the possibility of collimating an atomic beam by the light field produced by the reflection of a plane wave from the internal surface of a metal cone. It has been shown that the radiation pressure can reduce the atomic-beam transverse velocities to the value of the order of 100 cm/s which corresponds to effective temperature of about 10−3 K. A method for producing collimated beams of cold atoms based on simultaneous deceleration and collimation of atomic beams by resonant laser radiation pressure is proposed.
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  • 18
    ISSN: 1432-0649
    Keywords: 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
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  • 19
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    Applied physics 61 (1995), S. 121-124 
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
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  • 20
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    Applied physics 61 (1995), S. 489-491 
    ISSN: 1432-0649
    Keywords: 42.65 ; 63.20 ; 78.30
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    Topics: Physics
    Notes: 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.
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  • 21
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    Applied physics 62 (1996), S. 309-311 
    ISSN: 1432-0649
    Keywords: 52.40 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 22
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
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  • 23
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    Applied physics 63 (1996), S. 47-50 
    ISSN: 1432-0649
    Keywords: 31.20.Nt ; 42.65 ; 42.70
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    Topics: Physics
    Notes: 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.
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  • 24
    ISSN: 1432-0649
    Keywords: 42.65 ; 51.70
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    Topics: Physics
    Notes: 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.
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  • 25
    ISSN: 1432-0649
    Keywords: 42.25.Bs ; 42.65 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
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  • 26
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 27
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    Keywords: 07.60 ; 42.65 ; 33.70
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    Topics: Physics
    Notes: 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.
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  • 28
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    Applied physics 34 (1984), S. 55-61 
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    Keywords: 42.65
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    Topics: Physics
    Notes: Abstract Transient parametric scattering is investigated theoretically using density matrix perturbation theory. Emphasis is placed on the effects of population and transverse or dephasing relaxation on the scattered parametric pulse durations. Pulse duration measurement provides important insight into the actual transient temporal behavior of four-wave mixing processes and is shown to be a potentially useful technique for the characterization of material time constants and incident pulse shape.
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  • 29
    ISSN: 1432-0649
    Keywords: 42.50 ; 42.65 ; 33
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    Topics: Physics
    Notes: Abstract The three-level probe spectroscopy of Doppler-broadened transitions in the presence of a standing wave pump laser is investigated through a diagrammatic method. A probe-response diagram is defined where the resonance positions versus the probe laser frequency and absorber velocity are plotted. The dressed atom description provides a convenient method for deriving the probe response diagram and calculating the position of the Doppler-free structures on the absorption spectrum, including the ac Stark shifts. We have interpreted probe spectra on the basis of the probe response diagram, presenting new features and giving a detailed physical interpretation of all the coherent effects appearing in the spectra. Population effects are not included in the dressed system analysis and are calculated on the basis of a semiclassical treatment, but the probe response diagram provides a complete interpretation of the involved phenomena.
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  • 30
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    Applied physics 31 (1983), S. 153-155 
    ISSN: 1432-0649
    Keywords: 33 ; 42.65
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    Topics: Physics
    Notes: Abstract We report on the multistep ionization process observed in CS2 vapour irradiated by 337 nm nitrogen laser light. We propose and discuss a model in which optical as well as collisional excitation are involved in the ionization process.
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  • 31
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    Applied physics 33 (1984), S. 51-56 
    ISSN: 1432-0649
    Keywords: 42.65 ; 78.20 ; 42.40
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    Topics: Physics
    Notes: Abstract A theoretical study is presented of a special case of stationary energy transfer in degenerate two-wave mixing in a reflection geometry. The two interacting beams consist of a beam and its first-order internal reflection component created at the boundary of a nonlinear medium. Numerical results obtained from the computer calculations are presented as graphs. It is found that, under suitable conditions, this phenomenon can be used to eliminate the multiple internal reflections.
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  • 32
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    Applied physics 33 (1984), S. 133-139 
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    Keywords: 33.80 ; 42.65
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    Notes: Abstract Anti-Stokes Raman laser experiments using metastable atomic Tl and Sn have been performed. The required metastable population inversion is generated by photodissociation of TlI and SnBr2 with KrF laser radiation. The Tl(Sn) system permits frequency up-conversion by 7793 cm−1 (17,163 cm−1). By optimization of system parameters, uv output energies up to 2.5 mJ (377 nm) and conversion efficiencies of more than 25% have been achieved for Tl. Further improvements and principal limitations will be discussed.
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  • 33
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  • 34
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    Applied physics 34 (1984), S. 107-122 
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    Keywords: 42.65 ; 71.20
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    Notes: Abstract A short review on the theoretical description of nonlinear optical phenomena which are caused by an electric polarization cubic in the electric field amplitudes is given. Then the microscopic theories for the calculation of the nonlinear susceptibility, especially in semiconductors, are briefly reported. After a short section on the bandstructure of IV–VI compounds in a magnetic field, the lineshapes of the coherent anti-Stokes radiation as a function of the magnetic field are discussed in detail. In the experimental part measurements of coherent anti-Stokes Raman scattering (CARS) in PbTe and PbSe epitaxial films are reported. We observed pure as well as combined spin flip transitions. These data and the results of additionally observed interbandtransitions were used in least squares fits and consistent sets of bandparameters of PbTe and PbSe were obtained.
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  • 35
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    Applied physics 29 (1982), S. 255-262 
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    Notes: Abstract CARS spectra of thev 1-band of SF6 and UF6 performed under (static) cell conditions and under supersonic jet expansion have been recorded. The cooling behavior in supersonic jet expansions has been demonstrated for both gases.
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  • 36
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    Applied physics 30 (1983), S. 157-159 
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    Notes: Abstract The experimental results on upconversion of λ=1.06 μm radiation to the near ultraviolet in rubidium vapors providing 12% photon efficiency are reported under twophoton resonance of the concerted and pump sum frequency.
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  • 37
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  • 38
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    Applied physics 29 (1982), S. 37-42 
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    Keywords: 42.65 ; 61.20
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    Notes: Abstract Noncollinear phase-matched nonresonant four-photon frequency mixingω p+ω p−ω L→ω s in crystals and aqueous solutions of LiCl, CsCl, KF, and KI is studied. The concentration of the aqueous solutions is varied between 0.5 mol/l and saturation. Picosecond laser pulses of a mode-locked Nd-glass laser are applied as pump pulses. The energy conversion of laser light at frequencyω L to frequencyω S is measured and the nonlinear susceptibilities χ(3) are calculated. The dependence of the hyperpolarizabilities on concentration is analysed and gives information on the solute-solvent interaction.
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  • 39
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    Applied physics 31 (1983), S. 191-192 
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    Notes: Abstract Phase-conjugate reflection at theP(12) CO2 line (λ=10.51 μm) has been obtained in gaseous SF6 with a power reflection, coefficient of 220% and an energy reflection coefficient of 115%.
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  • 40
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  • 41
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    Keywords: 50 ; 34 ; 32.50 ; 42.60 ; 61.80 ; 62 ; 42.65
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  • 42
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    Applied physics 30 (1983), S. 189-193 
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    Keywords: 06.30 ; 42.65 ; 73.30
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    Notes: Abstract Frequency differences of up to 900 GHz between two laser lines near 568 nm were measured by mixing laser light and harmonics of 90 GHz microwave radiation. The Schottky point contact diodes used consisted of tungsten tips onn-GaAs bases with different degrees of doping. The formation of the contacts and the sensitivity and frequency limitations of the device are discussed.
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  • 43
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    Keywords: 32 ; 35 ; 42.65 ; 32 ; 33 ; 42.60
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  • 44
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  • 45
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  • 46
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    Applied physics 35 (1984), S. 59-64 
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    Notes: Abstract The observation of chaos in a hybrid optical bistable device is reported. There is no delay line in this system. An investigation of the mechanism concentrates on a somewhat simplified structure. This structure is described by a third-order differential equation with quadratic nonlinearity. Its realization as an electronic circuit is studied in detail. As we observe patterns of universal behaviour, we also comment on the relation to iterative maps.
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  • 47
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    Applied physics 26 (1981), S. 67-72 
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    Notes: Abstract Polarization decay in the presence of a standing electromagnetic wave field at a Doppler broadened transition is investigated theoretically and experimentally. It is shown that in the direction opposite to the propagation of an excited pulse the polarization decays at a transition frequency rather than at an exciting field frequency as usual. This permits the use of transients both in studies of relaxation processes and in Doppler-free super-high resolution spectroscopy. A resonant coherent transient has been used in measurements of relaxation decay constants of a dipole moment for collisions in SF6 (λ=10.6μm). This method has enabled one to resolve reliably the structure of theQ(38) transition (λ=10.6μm) of theF 1 0 +E 0=F 2 0 line of the 0→v 3 band in SF6 within a Doppler absorption line.
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  • 48
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    Applied physics 26 (1981), S. 105-110 
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    Notes: Abstract We present an analysis of the impulse response of four-wave mixing, in the case where the “two-photon term” of the nonlinear susceptibility is dominant. The nonlinear interaction itself will be considered to be steady state. The conditions of negligible pump depletion are considered first. It is shown that the reflected beam has only the character of perfect phase conjugation if the pulse length is longer than the medium length, and the latter is short compared to the characteristic distance of the problem. The “weak-pulse” approximation involving only two coupled equations is compared to the exact four-wave solution, when the medium thickness approaches the critical oscillation threshold. Finally, the stability and existence of steady-state solutions is analyzed for very long media (compared with the oscillation length).
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  • 49
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    Applied physics 29 (1982), S. 31-36 
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    Notes: Abstract Coherent anti-Stokes Raman spectroscopy (CARS) was used to measure the vibrational temperature of microwave-excited nitrogen in a N2−CO−He mixture. CARS spectra, originating from the N2-vibrational levelsv=0 up tov=3, have been recorded by both narrowband scanning of the resonance region as well as by broadband OSA detection. For the microwave-excited N2 molecules a vibrational temperatureT v (N 2 = (2130±110K) and a lower limit of detection forN 2(v = 3) = 1.2 x 1015 cm−3 was established. The CARS results were independently confirmed by simultaneously recorded and spectrally resolved CO infrared fluorescence studies.
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  • 50
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    Applied physics 29 (1982), S. 79-87 
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    Notes: Abstract By use of circularly polarized light we have exploited optical pumping within the Zeeman sublevels of the ground state to obtain optical bistability in sodium vapours with low threshold power (around 1 mW) and a wide tuning range (〉12 GHz). Experimental results are presented for different conditions of operation and compared to computer calculations, that include propagation effects and inhomogeneous broadening, based on a three-level atomic model that accounts for optical pumping.
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    Applied physics 33 (1984), S. 161-165 
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    Notes: Abstract Wavefront reflectivity in a conventional degenerate four-wave mixing (FWM) configuration can be calculated, using either approximate formulae, or exact numerical methods to solve the nonlinear coupled-wave equations. We have computed the wavefront reflectivity for FWM in a transmission and reflection geometry, respectively, using these two different methods. A comparison between them indicates that these formulae are reasonable approximations when beam coupling, diffraction efficiency and absorption are all low, and especially in the case of transmission geometry.
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  • 52
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    Applied physics 35 (1984), S. 17-21 
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    Keywords: 42.70 ; 42.65 ; 42.80
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    Notes: Abstract Anisotropic selfdiffraction in BaTiO3 crystals utilizing the large electrooptic coefficientr 42 is described. In the absence of an external electric field the generated space charge field is determined by diffusion processes. The theory is in agreement with the experimental results. The angles between extraordinary and ordinary beams, the intensity and time dependence of transmitted and diffracted beams, and phase conjugation effects are measured and evaluated.
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  • 53
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    Applied physics 60 (1995), S. 61-65 
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    Keywords: 32.00 ; 42.65 ; 82.50
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    Notes: 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.
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  • 54
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    Applied physics 61 (1995), S. 73-80 
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    Notes: 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.
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  • 55
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    Applied physics 61 (1995), S. 127-134 
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    Notes: 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.
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  • 56
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    Notes: 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.
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  • 57
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    Notes: 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).
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  • 58
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    Notes: 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.
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  • 59
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    Applied physics 61 (1995), S. 511-514 
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    Notes: 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.
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  • 60
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    Applied physics 62 (1996), S. 479-483 
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    Notes: 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.
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  • 61
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    Notes: 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.
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  • 62
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    Applied physics 63 (1996), S. 145-150 
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    Notes: 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.
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  • 63
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    Applied physics 63 (1996), S. 117-120 
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    Keywords: 42.60B ; 42.60D ; 42.65
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    Notes: 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.
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  • 64
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    Notes: 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.
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  • 65
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    Notes: 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.
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    Applied physics 30 (1983), S. 53-55 
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    Notes: Abstract The effective upconversion of CO2-laser radiation to the uv spectral range has been obtained in sodium vapors, the photon efficiency being 65%, the corresponding power efficiency being 2640%.
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  • 67
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    Notes: Abstract We report detailed experimental data on the passive Q-switching operation in a CO2 laser with CH3I saturable absorber, and on the transient behaviour in the near-Q-switching situation. Under suitable operating conditions, we found bistability in the output power. In some cases, we observed the simultaneous presence of bistability and passive Q-switching. The theoretical part of the paper starts from the four-level model of laser with saturable absorber, as formulated by other authors. By adiabatically eliminating the variables of the resonant levels, we reduce the problem to a set of three differential equations, from which we derive explicit analytical conditions for the rise of passive Q-switching. These conditions turn out to be in good qualitative and partially quantitative agreement with our experimental findings as well as with other experimental data previously obtained by other authors. Finally we classify the possible combinations of passive Q-switching and bistability that one can find in this type of experiments.
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    Applied physics 61 (1995), S. 49-57 
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    Keywords: 33.20 ; 42.65
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    Notes: 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.
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  • 69
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    Notes: 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.
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    Applied physics 61 (1995), S. 213-215 
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    Notes: 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.
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    Notes: 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.
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    Applied physics 61 (1995), S. 415-419 
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    Keywords: 42.65 ; 72.40 ; 78.20
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    Notes: 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.
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  • 73
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    Applied physics 60 (1995), S. 437-442 
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.65 ; 42.60
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    Topics: Physics
    Notes: 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.
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  • 74
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    Topics: Physics
    Notes: 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.
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  • 75
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    Applied physics 60 (1995), S. 571-572 
    ISSN: 1432-0649
    Keywords: 42.65 ; 72.70
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    Topics: Physics
    Notes: 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.
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  • 76
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    Topics: Physics
    Notes: 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.
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  • 77
    ISSN: 1432-0649
    Keywords: 33.00 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 78
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    Applied physics 61 (1995), S. 569-579 
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 79
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    Applied physics 62 (1996), S. 59-64 
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.65 ; 78.30
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    Topics: Physics
    Notes: 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.
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  • 80
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    Applied physics 62 (1996), S. 139-142 
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    Topics: Physics
    Notes: 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.
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  • 81
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    Applied physics 62 (1996), S. 293-297 
    ISSN: 1432-0649
    Keywords: 42.10 ; 42.65 ; 42.70
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    Topics: Physics
    Notes: 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.
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  • 82
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    Biology and fertility of soils 28 (1999), S. 204-211 
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Balances between nutrients applied or mineralized and nutrients removed in maize grain and stover were calculated in a hedgerow intercropping experiment in which Leucaena leucocephala and L. pallida prunings and cattle manure were applied. Hedgerow intercropping (also called alley cropping) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. In control treatments, nutrient depletion per season was in the order of 7–19 kg N ha–1, 4–12 kg P ha–1, 10–26 kg K ha–1, 0–2 kg Ca ha–1 and 3–6 kg Mg ha–1. N fertilizer reversed the depletion of N, but it accelerated the depletion of the other nutrients. Manure and at least two applications of leucaena prunings resulted in net positive balances of N, K, and Ca between amounts applied or mineralized and amounts removed by maize. The amounts of P and Mg applied with, or mineralized from, prunings or manure were insufficient to offset the negative balances of these nutrients.
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  • 83
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    Biology and fertility of soils 28 (1999), S. 182-195 
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus ; Intercropping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  A litter bag technique was used to study the decomposition and release of N, P, K, Ca, and Mg from Leucaena leucocephala and L. pallida prunings and cattle manure in a hedgerow intercropping trial conducted in the Ethiopian highlands. Hedgerow intercropping (also called alley cropping or alley farming) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. Manure was the most resistant to decomposition, losing only 15% of its dry matter (DM) in 15 weeks, compared to 41–57% lost by leucaena prunings. Large quantities of K (up to 104 kg ha–1) were mineralized from prunings and manure, but Ca and Mg were mostly immobilized. More N and P were released from prunings than from manure, which resulted in net immobilization of these nutrients in the initial stages of decomposition and net mineralization in later stages. Between the leucaenas more N was mineralized and less Ca and Mg were immobilized when L. leucocephala prunings were applied than when L. pallida prunings were applied. Fertilizer N increased DM decomposition and N mineralization. Mineralization of the nutrients was constrained by lignin and polyphenol contents. It is concluded that leucaena mulch and cattle manure may be significant sources of N and K for crop growth, but external sources of P, Ca and Mg may be required, particularly in acid soils which have low contents of these nutrients. However, this fertility effect has to be evaluated against the competition effect of trees to predict crop response.
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  • 84
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus ; Leaf pruning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of Leucaena leucocephala and L. pallida prunings and cattle manure on maize nutrient uptake and yield were investigated in a hedgerow intercropping trial in the Ethiopian highlands. Hedgerow intercropping (also called alley cropping) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. For each leucaena species, the experiment had 16 treatments resulting from a factorial combination of four levels of leucaena leaf prunings (no prunings applied; first prunings applied; first and second prunings applied; first, second and third prunings applied), two levels of air-dried cattle manure (0 and 3 t dry matter ha–1) and two levels of N fertilizer (0 and 40 kg N ha–1 as urea). Uptake of N, P and K increased significantly with application of the three nutrient sources, but uptake of Ca and Mg either did not respond or decreased with application of prunings and manure. All the three factors increased maize grain and stover yields significantly, usually with no significant interactions between the factors. At least two applications of prunings were required to significantly increase nutrient uptake and maize yield. Maize in the row closest to the hedge did not respond to these nutrient inputs. It is concluded that hedgerow intercropping, with or without manure application, can increase crop yields moderately (to 2–3 t ha–1 maize grain yields) in the highlands, but P, Ca and Mg may have to be supplied from external sources if they are deficient in the soil. Additional N is still required for higher yields (〉4 t ha–1 maize grain yields). However, quantification of the competition effects of the trees is also required to confirm these results.
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  • 85
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    Applied physics 31 (1983), S. 193-199 
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    Keywords: 42.60 ; 42.65
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    Topics: Physics
    Notes: Abstract It is shown that LiF crystals with F 2 − colour centers may be used in lasers for cavity Q-switching and in high-power Nd: glass laser systems for, increasing the contrast and the self-excitation threshold. Also Lif crystals with F 2 − centers are successfully used for the generation of ultrashort pulses, for the generation of difference frequencies in the ir spectral range and in intracavity spectroscopy experiments.
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  • 86
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    Applied physics 32 (1983), S. 49-52 
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    Topics: Physics
    Notes: Abstract Methods for simultaneous measurements of more than one flow velocity component using coherent Raman spectroscopy are proposed. It is demonstrated that using a kilowatt broad-band probe pulse (3–30 GHz) along with a megawatt narrow-band pump pulse (∼100 MHz), coherent Raman signal resulting from a single laser pulse is sufficient to produce a high-resolution Raman spectrum for a velocity measurement.
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  • 87
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    Topics: Physics
    Notes: Abstract We report the observation of coherent uv emission at 330.2±0.5 nm when sodium vapor in a heatpipe is irradiated with a pulsed visible dye laser with output wavelength in the 570–595 nm region. It is found that intense uv emission can be produced from Na atoms as well as from Na2 molecules. The excitation functions and their dependence on vapor density and laser power density are presented and the mechanisms for producing the emission are discussed.
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    Applied physics 27 (1982), S. 141-144 
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    Topics: Physics
    Notes: Abstract We observed a polarization change induced by laser radiation in the Raman-type three-level atom In in the presence of Ar. The observed two components in the polarization change spectrum of the probe beam correspond to the resonant Raman scattering and the luminescence processes in the spontaneous emission. The dependence of their intensities on the collision with Ar atoms agrees with the theory.
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  • 89
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    Applied physics 28 (1982), S. 25-29 
    ISSN: 1432-0649
    Keywords: 42.65 ; 06.60.Jn ; 32.80
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    Topics: Physics
    Notes: Abstract A new nonlinear correlation method which makes it possible to measure the duration of uv ultrashort pulses has been proposed. In this method the multiphoton ionization of gases is used as a nonlinear process and the ion current caused by the process is detected. We have also experimentally demonstrated its usefulness in the uv region by observing the second- and the third-order auto-correlation profiles of picosecond pulses at 2661 Å (the fourth harmonic of a mode-locked YAG laser), using NO and Xe gases, respectively.
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    Applied physics 60 (1995), S. 5-10 
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    Keywords: 42.65 ; 33.20
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    Topics: Physics
    Notes: 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.
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  • 91
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    Topics: Physics
    Notes: 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.
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  • 92
    ISSN: 1432-0649
    Keywords: 07.65 ; 33.00 ; 42.60 ; 42.65 ; 42.80
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    Topics: Physics
    Notes: 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.
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  • 93
    ISSN: 1432-0649
    Keywords: 33.10 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 94
    ISSN: 1432-0649
    Keywords: 42.30 ; 42.65 ; 42.70 ; 42.40
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    Topics: Physics
    Notes: 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.
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  • 95
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    Applied physics 62 (1996), S. 389-397 
    ISSN: 1432-0649
    Keywords: 02.60.Cb ; 02.70.-c ; 42.10 ; 42.25.Bs ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
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  • 96
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    Topics: Physics
    Notes: 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.
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  • 97
    ISSN: 1432-0649
    Keywords: 07.62 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 98
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    Applied physics 63 (1996), S. 161-166 
    ISSN: 1432-0649
    Keywords: 42.20 ; 42.30 ; 42.65
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    Topics: Physics
    Notes: 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.
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  • 99
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    Applied physics 63 (1996), S. 237-242 
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.65 ; 42.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
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  • 100
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    Keywords: 42.65
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    Topics: Physics
    Notes: 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.
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