Measurements of nonlinear absorption of intense 10 µm laser pulses in n-Ge, GaAs, and ZnSe

Abstract

We study the nonlinear absorption of high-power 10 µm radiation propagating through $n$-Ge, GaAs, and ZnSe materials widely used in the long-wave infrared range. Measurements are performed using both nanosecond and picosecond ${{\rm{CO}}_2}$ laser pulses providing intensities up to $100\;{\rm{MW}}/{\rm{cm}}^2$ and $5\;{\rm{GW}}/{\rm{cm}}^2$, respectively. Nonlinear absorption coefficients in optical quality $n$-Ge are found to be the same for both pulse durations. The nonlinear absorption coefficient of these materials scales inverse proportionally to their bandgap energies, indicating increased photoionization in the smaller bandgap materials.