Transient Reflectivity of Gallium Films Induced by Femtosecond Laser

Abstract

The transient reflectivity of gallium films induced by 150fs laser pulses has been studied by the pump-probe technique at the pump intensities of 109-1012W/cm2. The time-resolved reflectivity rise of the femtosecond probe in the first 1-4ps after the pump pulse excitation depends strongly on the pump pulse intensity. We demonstrate that the transient electron-phonon collision rate extracted from the reflectivity data is a strong function of the temperature, and thus the laser intensity. This collision rate is drastically different from that observed under equilibrium conditions. The scenario for the microscopic kinetics of the phase transition on the femtosecond time scale is discussed, and new experiments for observation of time-resolved optical properties are proposed. Show more