The recombination lifetime in CdSxSe1−xsemiconductor‐doped glass was measured by time‐resolved photoluminescence. It was found that long‐term exposure of the glass to high‐intensity laser pulses produced a permanent reduction of the free‐carrier lifetime from 80 ps to less than 10 ps. This change could be reversed by thermal annealing and should have applications to ultrafast optical signal processing.