Stimulated Brillouin scattering in magnetized direct-gap semiconductors.

Abstract

Following the time-dependent perturbation technique for the density matrix, the phenomenon of stimulated Brillouin scattering (SBS) has been analytically studied in weakly noncentrosymmetric (NCS) crystals like InSb immersed in a moderately strong magnetostatic field. The twofold role of the magnetostatic field B in terms of the sharpening of the density of states and Landau-level splitting have been examined quantum mechanically. The extremely large value of the spectroscopic splitting factor (${\mathit{g}}_{\mathit{c}}$-${\mathit{g}}_{\mathit{v}}$) and the very low electron and hole effective masses play the key roles in the significant enhancement in Brillouin susceptibility ${\mathrm{\ensuremath{\chi}}}_{\mathbf{B}}$, even when B is reasonably low. The origin of the NCS effect has been assumed to be in the parity indefiniteness of the energy states in the crystals exhibiting lack of inversion symmetry. We have considered near-resonant band-to-band electron transition in the direct-gap crystals to reduce to a simple one-dimensional problem in the presence of the magnetostatic field. Numerical estimates have been made for the InSb crystal at 77 K, duly irradiated by a pulsed 5.3 \ensuremath{\mu}m CO laser. The SBS threshold is found to be well below the crystal damage threshold and ${\mathrm{\ensuremath{\chi}}}_{\mathbf{B}}$ is found to be appreciably large. The results support strongly the candidacy of InSb for establishing itself as a promising crystal for strong SBS and optical-phase conjugation while immersed in a moderate magnetostatic field.