Two-photon absorption in semiconductors with picosecond laser pulses

Abstract

Single pulses from a well-calibrated mode-locked YAlG:Nd laser have been used to measure the two-photon absorption coefficient at 1.064 \ensuremath{\mu}m in several semiconductors. The materials studied are four direct-gap semiconductors, GaAs, CdTe, ZnTe, and CdSe, and one indirect-gap semiconductor, GaP. The results for the direct-gap semiconductors are interpreted with respect to the imaginary part of the third-order nonlinear susceptibility ${\ensuremath{\chi}}_{1111}^{(3)}(\ensuremath{-}\ensuremath{\omega},\ensuremath{\omega},\ensuremath{\omega},\ensuremath{-}\ensuremath{\omega})$. An anisotropy of the two-photon absorption coefficient is observed in GaAs.