High-intensity CO_2 laser interactions with indium antimonide

Abstract

The interaction of picosecond CO2 laser pulses with intrinsic and doped indium antimonide at high intensities is investigated both experimentally and theoretically. A consistent theory is presented that explains the phenomena of high-density carrier generation, transient reflectivity, and melting in the semiconductor. All physical parameters become highly nonlinear at high laser intensities and carrier densities. Account was taken of the dynamic energy band-gap shift, changes in the multiphoton absorption cross section and the effective mass of the electron, dynamic reflectivity, and transmission. Keldysh nonlinear carrier generation is found to be essential to explain the experimental observations. The spark formation threshold of both intrinsic and doped InSb was measured to be 4.3 GW/cm2, corresponding to an energy fluence threshold of 0.26 J/cm2, at a laser pulse duration of 45 psec. The pulse duration scaling of the damage threshold is also discussed.