THERMAL NONLINEAR EFFECTS WITH FREESTANDING GRATING WAVE-GUIDE STRUCTURES

Periodically corrugated wave guides consisting of a ZnS layer clad on one side by Al have been made free standing by deposition on to photor esist followed by removal of the photoresist using a solvent. Coupling of laser light into guided modes causes heating of the sample which l eads to a new nonlinear effect, namely, a surface distortion thermally induced by differences in expansion between the ZnS and the Al layers . A temperature rise of 5.4-degrees-C is sufficient to give strong eff ects in the intensity of the reflected beam. This phenomenon has been studied in detail for two samples with time resolved experiments allow ing the speed of response to be found.