Pump fluence dependence of ultrafast carrier dynamics in bulk ZnSe

摘要

Ultrafast carrier dynamics of bulk ZnSe is investigated by means of the optical-pump terahertz-probe spectroscopy with pump fluence ranging from 38 to 239 μJ/cm~2 at room temperature. With the laser pulse excitation at 400 nm, the negative transmission of terahertz pulse shows an ultrafast rising followed by a biexponential recovery. The relaxation time of fast decay and slow one is increased with pump fluence. This trend is expected for surface states filling, which may inhibit carrier lifetime.