Abstract

CdSe samples have been photoexcited with λ = 0.53 µm, 40 ps pulses and probed in reflection with λ = 2.8 µm pulses generated by second-order stimulated Raman scattering of λ = 1.06 µm pulses in methane. Besides the Drude like free carrier response, whose temporal characteristics are governed by plasma diffusion and recombination, the reflectivity shows features which are attributed to defects and/or impurities. These features depend on the orientation of the polarization relative to the crystal axis. A model correlating the reflectivity kinetics to the trapping of carriers in defects/impurity levels is going to be discussed.

© 1990 Optical Society of America