Nonlinear absorption spectroscopy of CdSe single crystals

An experimental investigation was made of the influence of laser radiation pulses on the spectral and time dependences of the transmission of CdSe single crystals at T = 4.2 K. The intensity of laser pulses transmitted by such a crystal was limited in the spectral region of the ground excited state because of two-photon absorption in which an exciton state acted as an intermediate level. A giant value of the two-photon absorption coefficient, amounting to ~ 10³ cm/MW, was obtained. The evolution of photoexcited nonequilibrium electron–hole pairs was investigated.