NONLINEARITY AND PHOTOSTRUCTURAL CHANGES IN GLASSY AS2S3 THIN-FILMS

Measurements are reported of the refractive index and absorption coeff icient changes of amorphous As2S3 (chalcogenide glass) thin films due to cw laser light irradiation. We have measured the transmittance thro ugh a thin film in the Z-scan technique configuration. Two different c ontributions to refractive index changes are demonstrated, showing the existence of a permanent and a dynamical effect. The first effect was demonstrated performing usual normal incidence transmittance measurem ents. The second dynamical change, revealed by the Z-scan technique, d isappears once the light source is turned off: measured in the latter case is a maximum change of the refractive index DELTAn = - 8 X 10(-3) in the cw regime at lambda = 5 14.5 nm.