LIGHT-INDUCED PERMANENT MODIFICATIONS OF THE NONLINEAR-OPTICAL PROPERTIES OF SEMICONDUCTOR-DOPED GLASSES

The nonlinear refractive index, n(2), and the two photon absorption co efficient, beta, of semiconductor doped glasses were experimentally in vestigated in the region of two photon absorption. We demonstrated tha t the magnitude and sign of the measured n(2) strongly depend on the p revious exposure of the sample to the laser radiation. For fresh (not exposed) samples the nonlinearity is negative and large. After repeate d measurements in the same spot, the magnitude of n(2) decreases, even tually becomes positive, and saturates to a value that approximates th e value expected from bulk semiconductor theory. Copyright (C) 1996 El sevier Science Ltd.