Transient gratings in InSb at two-photon excitation

We report a study of transient phase grating in InSb at room temperature induced by two-photon absorption of pulsed CO<
2
laser radiation. From our results, we deduce a value of the ambipolar diffusion coefficient
D \simeq 26
cm
²
. s
^-1
and of the lifetime of carriers
T_{R} \simeq 54
ns. The behavior of the grating and the change of refractive index confirms the free-carrier plasma being dominant in the modulation of nonlinear optical properties.