Multiphoton photoconductivity and optical nonlinearities in ZnSe and CdSe direct band gap crystals

摘要

The multiphoton photoconductivity properties of ZnSe and CdSe direct band gap crystals have been studied using frequency-doubled Nd: YAG laser excitation. Two-photon absorption in both crystals has been observed. The photoconductivity measurements and nonlinearity in Z-scan traces confirms the existence of a lower valence band, from where one-photon transitions are forbidden but two-photon transitions are allowed. The value of the two-photon absorption cross section gamma(2) in both crystals has been calculated by using second-order time-dependent perturbation theory.