Nonlinear optical measurements of hot carrier induced quadratic electrooptic effect in dc-biased semiconductor

Abstract

Fast optical nonlinearities which arise in dc-biased GaAs crystal have been investigated numerically and experimentally using the time-resolved picosecond four-wave mixing technique. Hot electron transport induced enhancement of optical nonlinearity as well as oscillatory behaviour of light diffraction efficiency in the subnanosecond time domain has been observed in the region of negative differential resistance. The kinetics of the four-wave mixing is compared with the numerical calculation of refractive index modulation taking into account coexisting free-carrier and quadratic electrooptic nonlinearities. The numerical modelling of hot electron dynamics in a spatially modulated GaAs crystal enabled us to explain the experimentally observed features and extract the modulation coefficient of quadratic electrooptic nonlinearity.