ABSTRACT
The influence of a quantizing electric field on the spin polarization is treated for semiconductor superlattices with a Rashba spin-orbit interaction. For weakly coupled superlattices, the quantum kinetic equation for the canonically transformed density matrix is analytically solved. The spin polarization, which is induced by a magnetic field via the Zeeman splitting, exhibits a sharp minimum at the cyclotron-Stark tunnelling resonance. This electric-field-induced resonant tunnelling mixes different spin states and leads to a strong spin depolarization.
ABSTRACT
A theoretical analysis is presented that describes wave-mixing processes in thin holographic gratings for phase-modulated beams. Experiments with photorefractive Bi(12)TiO(20) crystals in which the signals for Bragg diffraction and for the first non-Bragg diffraction order were measured support the analysis.
ABSTRACT
We show that a constant component of the holographic current may emerge in photorefractive crystals even in the absence of an applied electric field if the recording pattern is oscillating in a definite law. We derive conditions on the oscillations for the effect to appear. For instance, a fringe pattern with an intensity I ~ 1 + m cos[kx + Delta cos omegat + delta cos(2omegat + phi)] is fitted (here x is a linear coordinate, t is time, and m, k, omega, and phi are constants). In this case the dc component is j(0) -sin phi. One can detect the relative phases of the harmonics by this means.
