MEASUREMENT OF FREE-CARRIER NONLINEARITIES IN ZNSE BASED ON THE Z-SCAN TECHNIQUE WITH A NANOSECOND LASER

Self-defocusing and nonlinear absorption resulting from two-photon-excited free charge carriers were observed in polycrystalline ZnSe at the low power density of approximately 30 MW/cm2 by use of the Z-scan technique with nanosecond laser pulses. The total carrier absorption cross section and the variation of refractive index per unit of photoexcited carrier density were estimated to be 0.80 +/- 0.10 X 10(-18) cm2 and 0.60 +/- 0.15 x 10(-21) cm3, respectively.