Abstract

The origin of optical nonlinearity in a semiconductor-doped glass at room temperature is studied using a pump-probe experimental technique. Glasses doped with semiconductor crystallites which are commercially known as sharp-cut color filters provide very interesting media for nonlinear signal processing because of their rapid response time (due to short carrier diffusion time) and large optical nonlinearity.¹ The output of a nitrogen laser is used to pump a tunable dye laser (pump) and a dye cell (probe continuum). The pump-induced changes in transmission of the broadband probe are recorded with a combination of a spectrometer and an optical multichannel analyzer. A 100-Å blue shift of the band edge is observed in a selenium ruby glass (100–1000-Å microcrystallites of CdS_1−x embedded in a borosilicate glass matrix, x = 0.7–0.9) with 4 μJ of the narrow bandwidth pump tuned to 5100 Å (band edge ≃ 5200 Å). Using a high energy continuum alone (2-μJ energy), a blue shift of ≃ 175 Å is observed. The blue shift of the band edge cannot arise from a pump-induced thermal effect that would instead bring about a red shift. The band-edge blue shift is evidence for efficient band filling by injected carriers. The measurement of the nonlinear index, using an interferometric technique, is under way.

© 1985 Optical Society of America