LASER-INDUCED DARKENING IN SEMICONDUCTOR-DOPED GLASSES

We have performed experiments to characterize permanent laser-induced darkening in CdS(x)Se1-x semiconductor-doped glasses with picosecond pulses as a function of fluence, repetition rate, and pulse width. We find that the darkening occurs by means of a nonlinear process that exhibits an anomalous dependence on pulse width. Transmission spectra show that the induced darkening is uniform over the spectral range from the absorption edge out to 820-mu-m. Darkening in a number of different glasses is compared. On the basis of our results we propose a mechanism that involves photoassisted trapping of electrons from the semiconductor microcrystallites into states within the glass host material.