The thresholds of laser-induced darkening in different optical and laser gl
asses irradiated by a 800nm, 120fs, 1kHz Ti:sapphire laser are reported for
the first time. The ESR spectra of irradiated glass show laser-induced dar
kening results from color-center generation. The glasses are transparent in
the wavelength of 800nm, so we suggest that color - center is generated th
rough multi-photon absorption.