Abstract

Knowledge of the temporal response of the materials with large third order nonlinearities is important for optical switching applications, and is particularly important in understanding the propagation of short pulses in optical fibers. By analyzing Raman scattering spectra along with intensity-induced polarization changes, Hellwarth et al. were able to estimate the relative electronic and nuclear contributions to the third order nonlinearities of a number of glasses¹. The nuclear contribution has to be associated with a slow temporal response. However in usual glasses, previous experiments performed in the time domain with short pulses (~ 100 fs) failed to demonstrate such a contribution. Very recently, using very short pulses (~ 35 fs) and exciting large and particular defined stretching modes of original glasses, Kang et al. were able to evidence such a contribution². Hereafter, we demonstrate that using 100 femtosecond pulses with a Time Resolved Heterodyne Optical Kerr Effect technique, it is possible to evidence a nuclear contribution of glasses in the time domain in usual conditions. In the glasses studied, the nuclear contribution varies from 15 to 20 %. The damped oscillation are in very good agreement with Raman spectra.

© 1998 IEEE