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.