A two-beam setup based on the totally reflecting prism coupler is shown to be a powerful means of characterizing light-induced refractive-index modifications in dielectric thin films. Rise and relaxation times and amplitudes of thin-film refractive-index variations can be measured. Some developments of the electromagnetic theory of prism coupling are presented for Gaussian incident beams. Measurements made on a single Ta2O5 layer deposited on a silica glass are presented. Relaxation times of a few milliseconds reveal the thermal origin of the phenomena. The thermal nonlinear coefficient of this Ta2O5 layer is nearly 10−15 m2/W.
© 1996 Optical Society of America
S. Monneret, S. Tisserand, F. Flory, and H. Rigneault, "Light-induced refractive-index modifications in dielectric thin films: experimental determination of relaxation time and amplitude," Appl. Opt. 35, 5013-5020 (1996)