Studies of high-speed optical switching in CdSe

We have observed high-speed optical switching based on the optical bistability of CdSe at low temperatures due both to induced absorption and to dispersion changes. Using a streak camera to record the response of a thin CdSe platelet to high-intensity dye-laser pulses at near-band-gap energies, we have studied these phenomena on a picosecond time scale and measured switching times of several hundred picoseconds. We attribute our observations to nonlinearities caused by exciton interactions in the semiconductor material. Finally, we discuss the part played in these phenomena by thermal and other dynamic effects.