Optical nonlinearities and photo-excited carrier lifetime in CdS at 532 nm

Bound-electronic and free-carrier optical nonlinearities, and relaxation of photo-excited free carriers in CdS have been investigated by the use of a single-beam Z-scan technique at 532 nm. Under pulsed radiation of 35-ps duration with the input irradiances up to 4.8 CW/cm(2), the two-photon absorption coefficient, the bound-electron nonlinear refractive index, the free-carrier absorption cross-section, and the change in the refractive index per unit carrier density are determined to be 5.4 +/- 0.8 cm/GW, -(5.3 +/- 0.8) x 10(13) cm(2)/W, (3.0 +/- 0.5) x 10(-17) cm(2) and -(0.8 +/- 0.1) x 10(-21) cm(3), respectively. By using these values in the open-aperture Z-scans conducted with 7-ns laser pulses, the carrier recombination time is extracted to be 3.6 +/- 0.7 ns. The measured parameters are compared to theoretical calculations. (C) 2001 Published by Elsevier Science B.V.