Nonlocal Photorefractive Screening from Hot Electron Velocity Saturation in Semiconductors

Intervalley scattering of hot electrons during high-field transport in transverse-field photorefractive quantum wells induces a nonlocal optical response in which photoinduced changes in the refractive index are spatially shifted relative to the optical stimulus, providing an avenue for optical gain. We demonstrate that the onset of the photorefractive phase shift coincides with the onset of velocity saturation. This nonlocal response is the high-resistivity consequence in semi-insulating semiconductors of the Gunn effect mechanism.