Contactless determination of the dominant photorefractive mobile charge by comparing cw and ps two-wave mixing

Abstract In a cw photorefractive two-wave mixing the space charge field is created by deep traps and mobile photocarriers, whereas on the picosecond time scale an internal Dember field is created via the mobility difference of electrons μ e and holes μ h , leading to a unique definition of the field direction. By comparing dependences of the two-wave mixing gain versus sample orientation in cw and ps experiments, dominant photocarriers in the cw case are determined contactlessly. The results are checked by a single beam experiment, using an externally applied field. Results for InP:Fe, GaAs:Cr, and GaAs:EL2 are given.