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  • 1
    Electronic Resource
    Electronic Resource
    Backscattering of ultrashort high intensity laser pulses from solid targets at oblique incidence (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 581-588 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Backreflection of short, intense laser pulses at oblique incidence on solid targets is explained with a model where a periodic electron density modulation acts as a diffraction grating. The pump and reflected electromagnetic waves drive through the ponderomotive force the grating, and the coupled system becomes parametrically unstable. The basic equations governing this situation are given. A linearized stability analysis is used to obtain the instability growth rate in a homogeneous plasma and the convective gain coefficients for the inhomogeneous case. The results support the feasibility of the suggested mechanism. An absolute instability is predicted to set on at a threshold intensity of about 1016 W/cm2 for a typical laser pulse with a length of 100 fs and a spot size of 30 μm. The instability is shown to saturate at a level of a few percent, because the higher harmonics in the electron density modulation make the diffraction more diffuse, thus reducing both the ponderomotive force and the backreflection coefficient. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1423620
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  • 2
    Electronic Resource
    Electronic Resource
    Waveguide propagation of intense electromagnetic radiation in slightly inhomogeneous nonlinear media (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 3 (1993), S. 107-115 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The propagation of self-localizing beams of electromagnetic waves in the form of nonlinear waveguides in a slightly inhomogeneous medium is studied analytically and numerically. The trajectories of the axial ray are studied as a function of its direction and the field strength at the initial point on the basis of a nonlinear scalar Helmholtz equation. Analytic expressions are derived. The longitudinal refractive index, the field intensity, and the waveguide radius are plotted as functions of the instantaneous position of the point on the axial ray. Deep penetration of the beam into the opaque region and the position of the screening surface are studied as functions of the parameters of the beam and the medium. A steady-state 3D problem is analyzed for a power-law nonlinearity with an arbitrary power. A 2D problem is analyzed for the case of a ponderomotive nonlinearity with saturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.165972
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  • 3
    Electronic Resource
    Electronic Resource
    Strain distributions in quantum dots of arbitrary shape (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 297-305 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method based on the Green's function technique for calculating strain in quantum dot (QD) structures has been developed. An analytical formula in the form of a Fourier series has been obtained for the strain tensor for arrays of QDs of arbitrary shape taking into account the anisotropy of elastic properties. Strain distributions using the anisotropic model for semiconductor QDs are compared to results of a simplified model in which the elastic properties are assumed to be isotropic. It is demonstrated that, in contrast to quantum wells, both anisotropic and isotropic models give similar results if the symmetry of the QD shape is less than or equal to the cubic symmetry of the crystal. The strain distribution for QDs in the shape of a sphere, cube, pyramid, hemisphere, truncated pyramid, and flat cylinder are calculated and analyzed. It is shown that the strain distributions in the major part of the QD structure are very similar for different shapes and that the characteristic value of the hydrostatic strain component depends only weakly on the QD shape. Application of the method can considerably simplify electronic structure calculations based on the envelope function method and plane wave expansion techniques. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370728
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  • 4
    Electronic Resource
    Electronic Resource
    Metal–n-6H–SiC surface barrier height—Experimental data and description in the traditional terms (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5511-5514 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work compares our experimental data on surface barrier height in structures metal–n-6H–SiC for several metals (Al, Au, Mo, Cr) with other data available and with classical models of surface barrier formation. We observed decreasing of barrier height with increasing of donors concentration for the structures Au–n-6H–SiC, Mo–n-6H–SiC and Al–n-6H–SiC. We estimate the average surface energy level for (0001)-Si-faced n-6H–SiC, appearing in capacitance–voltage (C–V) measurements, to be about 0.3Eg at room temperature (Eg is the energy band gap) and corresponding surface states density to be about 1013 cm−2 eV−1, based both on our data and data of other authors. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359668
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  • 5
    Electronic Resource
    Electronic Resource
    Optical absorption in PbSe spherical quantum dots embedded in glass matrix (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 750-757 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A phosphate glass embedded with PbSe semiconductor quantum dots (QDs) has been synthesized and investigated. Optical absorption spectra of PbSe spherical QDs have been studied both theoretically and experimentally. Theoretical analysis of the energy spectra and optical transitions has been carried out in the framework of four-band k⋅p model taking full account of anisotropy effects. It is demonstrated that the strong anisotropy of the energy bands of bulk PbSe gives rise to additional optical transitions in the quantum dots. These anisotropy-induced optical transitions have been clearly observed in the measured absorption spectra of the PbSe quantum dots. The calculated energy positions of the optical transitions are in good agreement with experiment. Five optical transitions were distinguished and interpreted in the absorption spectra measured at T=12 K. For the set of samples with a narrow size distribution of PbSe QDs (diameters in range of 40–110 Å), the energies of three or four optical transitions have been determined from the measured absorption spectra at T=300 K. The calculated dependencies of the energies of the first five optical transitions with QD size are in good agreement with those obtained from the experimental data. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373733
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  • 6
    Electronic Resource
    Electronic Resource
    5f magnetism in (U,Th)CoSn (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3070-3072 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As part of an investigation of UTX compounds (T represents a transition metal and X represents an element out of the group Al, Ga, Sn) we performed magnetic susceptibility, magnetization, and specific-heat measurements on the pseudoternary system (U,Th)CoSn. The results are discussed in terms of a varying 5f-electron density of states at EF which is controlled by the U concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340899
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  • 7
    Electronic Resource
    Electronic Resource
    Energy level correlations in disordered metals: Beyond universality (1996)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 37 (1996), S. 4968-4985 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: This short review is concerned with energy level statistics in weakly disordered metallic grains. In particular, we concentrate on how these statistics deviate from the universal ones. Using a nonperturbative approach we evaluate the large frequency asymptotics of the two-point correlator of the density of states. This allows us to describe the behavior of the system at arbitrary times. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.531674
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  • 8
    Electronic Resource
    Electronic Resource
    Millimeter-wave response and linewidth of Josephson oscillations in YBa2Cu3O7 step-edge junctions (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1295-1297 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the response of YBa2Cu3O7 step-edge junctions to low-intensity millimeter-wave radiation in the temperature range from 4 to 80 K. The linewidth of the Josephson oscillations derived from the resonant part of the response at voltages V(approximately-equal-to)(h/2e)f is shown to be determined by thermal fluctuations at liquid nitrogen temperatures. At lower temperatures the observed linewidth increases indicating that low-frequency fluctuations become dominant in the junction as the temperature is reduced. Due to an inhomogeneous spatial distribution of the current the step-edge junction might be considered as a multijunction multiloop interferometer and the excess noise can be discussed in terms of spontaneous transitions between the different states of these interferometers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108712
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical performance and structure optimization of 3.5–4.5 μm InGaSb/InGaAlSb multiple-quantum-well lasers (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2640-2642 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comprehensive theoretical investigation to optimize 3.5–4.5 μm InGaSb/InGaAlSb quantum-well (QW) lasers grown on ternary InGaSb substrates. We use an eight-band k⋅P Hamiltonian to calculate the Auger recombination and optical absorption coefficients in the active region, as well as the gain and threshold characteristics. The dominant Auger process involves hole excitation from the QW to unbound valence states. For structure optimization we varied the Ga content in the substrate and QW barrier layers. The optimized structure was obtained by maximizing the strain in the QWs, despite the Auger coefficient also increasing with strain. It is, therefore, demonstrated that the main aim for midinfrared laser optimization can be minimization of the threshold carrier density rather than reduction of the Auger coefficient. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1369146
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  • 10
    Electronic Resource
    Electronic Resource
    Inductance mode characteristics of a ceramic YBa2Cu3O7−x radio-frequency superconducting quantum interference device at 77 K (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3572-3575 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results on some radio-frequency superconducting quantum interference device (rf-SQUID) signal properties are presented. The quantum interferometer was made of ceramic YBa2Cu3O7−x and was due to a low critical current operated in the inductance or nonhysteretic mode. With bias current as reference, amplitude variation, and phase shift of the voltage over the tank circuit coupled to the SQUID were measured simultaneously. It is shown that there is qualitative agreement between calculations based on the resistivity shunted junction model and the data. Moreover, using phase detection, signal instabilities predicted for the rf-SQUID inductance mode were observed. These signal instabilities may be exploited to enhance the transfer coefficient for measured flux-to-output signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354537
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