A. I. Shkrebtii

Quantum interference control of currents in CdSe with a single optical beam

We show that ballistic current generation can occur in a semiconductor via quantum interference between absorption pathways for orthogonal polarization components of a single-frequency beam. This effect occurs for a subset of noncentrosymmetric materials, is macroscopically associated with a second-order nonlinear optical susceptibility, and produces current injection linearly proportional to the beam intensity. We demonstrate this in wurtzite CdSe (Eg=1.75 eV) at 295 K using cw and femtosecond optical sources of wavelength 600–750 nm (2.07–1.66 eV). The intensity and spectral dependence are in reasonable agreement with a first-principles calculation. Continuous current density of 30 μA cm−2 is produced for 60 mW cm−2 intensity at 633 nm.

Polarization-dependent surface transitions at Sb/GaAs (110)

We have investigated, both experimentally and theoretically, the optical properties of an epitaxial monolayer of Sb deposited on GaAs(110). In particular we have studied the polarization-dependence of Differential Reflectance. Good agreement between the experimental results and theory has been found. Several spectral features observed in the visible energy range have been interpreted, on the basis of the theoretical results, as optical transitions taking place at different symmetry points of the surface Brillouin zone.

Three color coherent generation and control of current in low-temperature-grown GaAs

We demonstrate coherent generation and control of electrical currents in low-temperature-grown GaAs at 300 K using three phase-related, 150 fs pulses derived from a parametric process. Interference between single photon (0.8 μm) and nondegenerate two photon (1.4 and 1.8 μm) absorption amplitudes generates ballistic electrical currents whose beam polarization dependence is in agreement with a simple Fermi’s golden rule calculation.

Issues Concerning the Calculation of the Optical Response of Semiconductors

We consider a number of issues crucial to the realistic calculation of the linear and nonlinear optical response of semiconductor surfaces, including problems related to unphysical, apparent divergences in the calculations, the strong sensitivity of the calculated response to wave function symmetry, the effect of local field corrections in supercell calculations, and new nonlinear optical phenomena related to coherent control.

Linear and non-linear spectroscopy of GaAs and GaP: theory versus experiment

Abstract We have calculated and compared the linear and non-linear optical response of GaAs and GaP bulk within three methods: ab-initio density functional theory (DFT); local density approximation (LDA)-based pseudopotential plane wave (PPW); and full-potential linearized augmented plane wave (FLAPW) approaches, together with the empirical tight-binding (ETB) method. Specifically, we have calculated the dielectric function and second harmonic generation (SHG) susceptibility over a broad frequency range. Important conclusions about the applicability of the ETB method for the calculation of bulk optical responses have been drawn with respect to the higher-order susceptibility.

Microscopic calculation of structure and optical properties of Ge(001)c(4×2)

Abstract We calculate the optical properties of the Ge(001) surface in the presence of the (2×1), p(2×2), and c(4×2) reconstructions. The atomic geometries of the higher-order c(4×2) and p(2×2) reconstructions have been determined from ab-initio molecular dynamics (MD). The calculated electron band structure fits the experimental data well; the metallic behavior can be explained only in terms of dimer dynamics. A serious discrepancy is found between the calculated and measured reflectance anisotropy; its possible reasons are discussed.

Coherent control of electron–hole populations in GaAs

The electron–hole generation rate in (111)-oriented GaAs is coherently controlled through the relative phase of absorbed 1550 and 775 nm, 120 fs pulses. Quantum interference between single- and two-photon transitions underlies this process which, in general, only occurs in noncentrosymmetric semiconductors since macroscopically it is related to a second-order susceptibility (χ(2)).