Photorefractive phase shift induced by hot-electron transport: multiple-quantum-well structures

Abstract

The photorefractive transport models that include hot-electron transport nonlinearities in the photorefractive transport equations introduce a new phase-shift mechanism that explains the large energy exchange recently observed in semi-insulating multiple-quantum-well structures during photorefractive beam coupling. We show that carrier heating by large applied electric fields contributes a nonlinear transport length that limits the magnitude of the space-charge electric field and introduces a photorefractive phase shift that can approach π/2. The nonlinear contribution is dependent on field strength and on fringe spacing and should be a general property of velocity saturation in the direct-gap semiconductors. These results may force a reinterpretation of apparent trap-limited behavior in bulk photorefractive semiconductors even under nonresonant excitation.