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  • 1
    Electronic Resource
    Electronic Resource
    Beam divergence effects on nonlinear frequency mixing (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1091-1101 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the beam divergence of the input pump laser beams on the nonlinear frequency mixing process in a dielectric medium is discussed. The divergent laser beams have finite angular spreads so that all of the interactions between the two input beams can never satisfy the phase-matching condition exactly. A numerical model is developed to investigate the effects of input beam divergence on conversion efficiency. The angular spread of each of the input beams is represented by a set of plane waves having a distribution of propagation directions. Each of the plane-wave components from one input beam is allowed to interact with all the plane-wave components of the second input beam. This model is applicable to processes such as sum frequency generation, difference frequency generation, and optical parametric amplification. Second-harmonic generations as a special case of sum frequency generation is used as an example in the numerical studies. Results indicate that the conversion efficiency is dependent on the amount of beam divergence, the input intensity, and the length of the nonlinear medium. These parameters must be optimized with respect to one another to maximize the conversion. The optimization is especially critical in high-power systems where high conversion efficiency is sought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351272
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  • 2
    Electronic Resource
    Electronic Resource
    Sustained rotational stabilization of DIII-D plasmas above the no-wall beta limit : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1997-2005 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice the stability limit calculated without a wall has been achieved in DIII-D by a combination of error field reduction and sufficient rotation drive. Previous experiments have transiently exceeded the no-wall beta limit. However, demonstration of sustained rotational stabilization has remained elusive because the rotation has been found to decay whenever the plasma is wall stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts a resonant response to error fields in a plasma approaching marginal stability to a low-n kink mode. Enhancement of magnetic nonaxisymmetry in the plasma leads to strong damping of the toroidal rotation, precisely in the high-beta regime where it is needed for stabilization. This resonant response, or "error field amplification" is demonstrated in DIII-D experiments: applied n=1 radial fields cause enhanced plasma response and strong rotation damping at beta above the no wall limit but have little effect at lower beta. The discovery of an error field amplification has led to sustained operation above the no-wall limit through improved magnetic field symmetrization using an external coil set. The required symmetrization is determined both by optimizing the external currents with respect to the plasma rotation and by use of feedback to detect and minimize the plasma response to nonaxisymmetric fields as beta increases. Ideal stability analysis and rotation braking experiments at different beta values show that beta is maintained 50% higher than the no wall stability limit for durations greater than 1 s, and approaches beta twice the no-wall limit in several cases, with steady-state rotation levels. The results suggest that improved magnetic-field symmetry could allow plasmas to be maintained well above no-wall beta limit for as long as sufficient torque is provided. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1446036
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  • 3
    Electronic Resource
    Electronic Resource
    A one-dimensional axial electron cyclotron resonance source model : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 666-668 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A conventional zero-dimensional (uniform plasma parameters with no spatial variations) fluid model will provide a good match with an experimental electron cyclotron resonance ion source (ECRIS) charge-state distribution (CSD) if provided with a judicious set of user inputs. However, this arbitrarily chosen set of inputs is not necessarily unique. To be truly predictive, an ECRIS model should rely on experimental parameters as inputs. A multi-species model for an ECRIS plasma using experimental parameters as inputs is under development. The model eliminates electron temperature as a user input by employing a 2 V(v,θ) Fokker–Planck code with an ECR heating term to calculate the non-Maxwellian anisotropic electron distribution function. Further arbitrary user inputs are eliminated in favor of controlled parameters by bounce averaging the Fokker–Planck coefficients for a one-dimensional (1D)/2 V axial model. The neutral gas modeling has been extended to 1D using axially coupled particle balance equations. The improved model is able to reproduce experimental Faraday cup (CSDA) from the Argonne National Laboratory's ECR-II. Further elimination of arbitrary inputs is expected when the ion model is extended to 1D. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150254
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  • 4
    Electronic Resource
    Electronic Resource
    Lateral mode behavior of reactive-ion-etched stable-resonator semiconductor lasers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4294-4296 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental results on monolithic stable-resonator semiconductor lasers. Curved end mirrors defining a near-concentric stable resonator were fabricated on wide-stripe GaAs/AlGaAs GRINSCH-SQW lasers using reactive-ion-etching. These lasers oscillate in close to the expected lowest-order Gaussian stable-resonator modes at threshold, evolving into a coherent superposition of higher-order modes as the pump current is increased up to two to three times threshold. At higher pump currents nonlinear defocusing effects cause the resonators to become geometrically unstable so that the lateral modes are determined by both the resonator geometry and the saturated gain and index profile. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359831
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  • 5
    Electronic Resource
    Electronic Resource
    Radius and current scaling of argon K-shell radiation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2781-2788 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Argon gas puff experiments on a 3–4 MA generator show that the K-shell x-ray yield is optimized for a 2.5 cm initial diameter and 110 ns implosion time. By varying the driver current, the K-shell yield varies from 13 to 18 kJ following a current to the fourth power scaling. Comparisons of these experimental data to one-dimensional radiation-hydrodynamic simulations with and without enhanced transport coefficients show that the measured K-shell yields exceed those predicted based solely on kinetic energy input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356217
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  • 6
    Electronic Resource
    Electronic Resource
    A magneto-optical study of interdiffusion in InGaAs/InP quantum wells: Effects of heat treatment, substrates, and dopants (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6826-6833 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interdiffusion in InGaAs/InP quantum wells has been studied using magneto-optical transmission spectroscopy. The effects of dopants in the substrates and quantum wells, overgrowth and annealing processes have been investigated, providing useful information on the interdiffusion effects in typical growth and fabrication processes. The blue shift effect which is often observed in multiple quantum well (MQW) structures subjected to heat treatment, is attributed to a dominant group V interdiffusion which can be suppressed by high defect densities in the substrate. The presence of Zn-dopants in an overgrown layer on top of the MQW structures causes a counteractive redshift effect after long annealing times due to group III diffusion, but in situ Zn- or S-dopants produce no observable shift in transition energies due to interdiffusion. This is attributed to enhanced group III interdiffusion induced by Zn diffusion into the MQWs. We conclude that there are very different interdiffusion mechanisms for group III and group V elements and support the recent suggestion of vacancy-related group V interdiffusion in contrast to the interstitialcy mechanism for the group III interdiffusion. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361504
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  • 7
    Electronic Resource
    Electronic Resource
    Eye-safe Nd:YAG laser (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 650-652 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated that a significant amount of laser energy can be extracted at 1.4444 μm from Nd:YAG at room temperature. The stimulated emission cross section at 1.4444 μm is not unduly small. More than 1 J of laser energy in the non-Q-switched mode and over 130 mJ with a pulse width of 85 ns full width at half maximum in the Q-switched mode have been obtained. The 1.4444 μm laser has also been operated successfully at repetition rates up to 10 Hz at the 100 mJ/pulse level. Other lasing transitions at 1.064, 1.3187, 1.3381, 1.3572, and 1.4150 μm have also been observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103621
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  • 8
    Electronic Resource
    Electronic Resource
    Electron field emission from SiC/Si heterostructures synthesized by carbon implantation using a metal vapor vacuum arc ion source (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1926-1928 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A remarkably low turn-on field of about 1 V/μm has been observed in electron field emission from planar SiC/Si heterostructures formed by high dose C implantation into Si using a metal vapor vacuum arc ion source. An implant energy of 35 keV was used to a dose of 1.0×1018 ions/cm2 with subsequent annealing in nitrogen at 1200 °C for 2 h. X-ray photoelectron spectroscopy showed that a thin surface stoichiometric SiC layer, with a thickness of about 150 nm, had been formed. Atomic force microscopy showed that there are densely distributed small protrusions formed on the surface. The formation of a thin surface stoichiometric SiC layer and the formation of densely distributed small protrusions on the surface are believed to be the two factors responsible for the efficient electron field emission.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121229
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic domain structures of Co22Ag78 granular films observed by magnetic force microscopy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 2472-2474 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetic force microscope (MFM) was used to image the topography and magnetic microstructures of Co22Ag78 granular films. The observed morphology shows isolated nanometer-scale cobalt particles (granules) embedded in the silver matrix. Stripe magnetic domains with much larger size (typically of ∼100 nm wide) than that of cobalt particles are resolved clearly on MFM micrographs for the annealed samples. It is demonstrated that the domain width and the relative magnetic force strength first increases and then decreases with annealing temperature with a maximum at about 600 K. We suggest that the appearance of the stripe domains is attributed to magnetic correlation among many of the isolated single-domain cobalt particles and is dependent on the microstructure of the samples. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121393
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  • 10
    Electronic Resource
    Electronic Resource
    Phonon-boundary scattering in thin silicon layers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1798-1800 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature fields in microdevices made from silicon-on-insulator (SOI) wafers are strongly influenced by the lateral thermal conductivity of the silicon overlayer, which is diminished by phonon scattering on the layer boundaries. This study measures the thermal conductivity of single-crystal silicon layers in SOI substrates at temperatures between 20 and 320 K using Joule heating and electrical-resistance thermometry in microfabricated structures. Data for layers of thickness between 0.4 and 1.6 μm demonstrate the large reduction resulting from phonon-boundary scattering, particularly at low temperatures, and are consistent with predictions based on the phonon Boltzmann transport equation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119402
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