Optical Nonlinearities and Switching from Excitons in II–VI Semiconductors

Coherent nonlinear resonances due to extended and localized excitons in CdSe and CdSe x S1-x have been investigated by picosecond time resolved degenerate four-wave mixing and differential transmission experiments. Large nonlinear coefficients (χ(3) ≥ 10 cm2/V2) are found, with coherence times in the picosecond range. Results on picosecond optical switching in CdSe are presented and discussed.