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  • 1
    Electronic Resource
    Electronic Resource
    The Auger recombination rate is larger in a GaSb quantum well than in bulk GaSb (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 836-840 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band-to-band Auger recombination rate in bulk GaSb and in a GaSb quantum well is calculated. It turns out to be larger in the quantum well because the threshold of the Auger process is located at the band edge where the density of states is larger in the quantum well than in bulk. A simple picture is developed to illustrate the physics of the Auger processes in bulk and quantum-well direct-band-gap semiconductors. With this picture, we propose that the composition-disorder-induced band mixing should be considered in order to explain the unusual behavior of the Auger process in an InGaAsP quantum-well structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347318
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  • 2
    Electronic Resource
    Electronic Resource
    Auger recombination in HgCdTe quantum wires and quantum boxes (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3394-3398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum-wire and quantum-box structures for narrow-gap materials with small effective masses, such as HgCdTe, can readily be fabricated using current lithographic techniques. In this article, we calculate the Auger-recombination carrier lifetimes in HgCdTe quantum-wire and quantum-box structures, with band gaps in the 2–5 μm wavelength range. Quantum confinement is generally believed to increase the carrier lifetimes. However, we find the Auger recombination lifetime in a HgCdTe quantum wire is shorter than that in a quantum well, and it decreases as the wire width decreases because of the corresponding increase in the density of states. On the other hand, band-to-band Auger recombination is zero in a quantum box because the overlap functions vanish and because of the discrete nature of the energy levels. Therefore, within the confines of our model, we can expect improved temperature performance from long-wavelength quantum-box lasers but not from quantum-wire lasers. Furthermore, these conclusions are applicable for all types of band-to-band Auger processes and semiconductor materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350935
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  • 3
    Electronic Resource
    Electronic Resource
    Carrier lifetimes and threshold currents in HgCdTe double heterostructure and multi-quantum-well lasers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6869-6875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Auger and radiative combination carrier lifetimes in HgCdTe bulk and quantum-well structures, with band gaps in the wavelength range 2–5 μm, are calculated. The Auger recombination rate in a HgCdTe quantum well (QW) is shown to be significantly smaller than that in bulk material. Threshold current densities of HgCdTe double-heterostructure (DH) and multiquantum-well (MQW) lasers are calculated. In a HgCdTe DH laser, Auger recombination dominates the carrier loss at threshold. In a HgCdTe MQW laser, on the other hand, radiative recombination dominates the carrier loss. MQW lasers shown improved temperature performance over conventional DH lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347676
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced exciton absorption and saturation limit in strained InGaAs/InP quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 769-772 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new approach for enhancing the exciton absorption and increasing the saturation limit in quantum wells (QWs), using tensile strain, is proposed. Because of the valence-band mixing in a strained QW, the in-plane hole mass can become very large or negative. This leads to a heavy electron-hole reduced mass (exciton mass), and therefore to a small exciton radius. Exciton absorption is substantially increased because of the increased electron-hole overlap probability in these small-radius excitons. The effects of saturation are also substantially reduced because of decreased charge-screening effects for small-radius excitons and because the rapid dispersal of the photon-generated excitons reduces the Pauli exclusion effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351341
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  • 5
    Electronic Resource
    Electronic Resource
    Improved performance of an optically pumped FIR laser using metallic waveguide : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4672-4674 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to improve the overall output characteristics of far-infrared (FIR) lasers, recent development at UCLA has concentrated on the use of a metallic overmoded waveguide (smooth bore and corrugated) instead of a conventional smooth-bore dielectric waveguide. The metallic waveguide has substantially lower propagation losses, especially at frequencies below 500 GHz, and also supports the desired HE11 mode. Laboratory results show a substantial increase in output power using a corrugated metallic waveguide, with 37 mW being obtained at 1.22 mm using 13CH3F (isotopic methyl fluoride) while maintaining the same mode quality and polarization. This represents an improvement of 100% over a smooth-bore dielectric waveguide. Comparison of far-infrared output using the three types of waveguide will be made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143659
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrafast stimulated emission spectroscopy of perylene in dilute solution: Measurement of ground state vibrational population relaxation (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 6075-6082 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report ultrafast stimulated emission measurements of perylene in a series of polar and nonpolar solvents. In all solvents the perylene stimulated emission spectra evolve in time. We observe individual features corresponding to distinct vibronic resonances in the stimulated emission spectra. The intensities of these features increase subsequent to excitation and persist for hundreds of picoseconds. The fast build-up seen at short delay times is related directly to the vibrational population relaxation time, T1 , of the ground vibrational state that is the lower energy state of the stimulated transition. The measured T1 times for perylene vary with both ground vibrational state and solvent. The slow decay rates for these data, the sum of the stimulated and spontaneous decay rates for the particular transition, depend critically on the particular transition that is resonant with the probe laser electric field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464846
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  • 7
    Electronic Resource
    Electronic Resource
    High-resolution deposition rate monitor (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 247-249 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 16-MHz piezoelectric quartz resonator has been used to build up a high-resolution deposition rate monitor. A direct counting allows a resolution of 1 ng/cm2 at a rate of one reading per second. Direct computer interface and increase in the voltage excitation above the plasma noise level have been successfully used to monitor the deposition rate in a dc sputtering apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144445
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  • 8
    Electronic Resource
    Electronic Resource
    Forbidden Auger process in strained InGaSb/AlGaSb quantum wells (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2922-2924 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carrier loss due to Auger recombination has been known to be the major factor limiting the performance of long-wavelength semiconductor lasers. We show for the first time that the dominant Auger process in InGaSb/AlGaSb and InGaAs/InP strained quantum well structures can be suppressed because of the conversation of energy and crystal momentum with the sufficient reduction of the in-plane heavy hole masses. As a result, low-threshold currents and good temperature performance can be achieved in strained quantum well semiconductor lasers. An analytic expression for the in-plane effective hole masses in a strained quantum well is derived and used to calculate the hole masses of InGaSb/AlGaSb strained quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103731
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  • 9
    Electronic Resource
    Electronic Resource
    Experimental apparatus for production, cooling, and storing multiply charged ions for charge-transfer measurements (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1931-1939 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel method is described that combines the production of ions by laser ablation with an ion-trap technique for the measurement of thermal-energy charge-transfer rates of multiply charged ions and neutrals. The charge-transfer rate is determined by measuring the rate of loss of stored ions from the trap. Verification of the calibration of the apparatus is demonstrated through investigation of charge transfer of N2 and N2+, which has been studied by another group. We also have made the first measurement on the thermal-energy charge-transfer coefficient of Ar and W2+. The rate coefficient is 0.99(0.22)×10−11 cm3 s−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141118
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  • 10
    Electronic Resource
    Electronic Resource
    Recent developments in optically pumped far-infrared lasers for plasma diagnostics (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3307-3307 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Optically pumped far-infrared (FIR) lasers are widely utilized in the diagnosis of fusion plasmas. Applications such as interferometry, polarimetry, and collective scattering all rely heavily on the characteristics of such lasers. In particular, the stability, available power, and wavelength of the FIR laser are extremely important in establishing system performance. This describes recent development work at UCLA directed at improving the above laser characteristics. Stability improvement is investigated via the use of a FIR ring cavity which automatically eliminates the feedback effects of CO2 pump radiation. Modifications in the optical design of both CO2 and FIR laser cavities have led to increased FIR output power. Finally, the use of a novel FIR output coupler and increased pump power has increased the number of high-power FIR wavelengths available for plasma diagnostic applications. This work was supported by U.S. DOE contract No. DE-FG03-86ER-53225.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141624
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