Abstract

We calculate the exact diffraction pattern in the far-field resulting from the incidence of focussed Gaussian beams on thin samples of Kerr-type and thermally nonlinear media. For the latter case, we model the temperature profile by using the heat equation with a source term proportional to the beam intensity. Our results show the essential differences between the effects of these two types of nonlinearities. Notably, the thermal non­linearity is responsible for a distinctive far-field on-axis minimum when the nonlinear sample is placed beyond the focus of the incident Gaussian beam. We have also verified this result experimentally by using a solution of chlorophyll in alcohol.

© 1992 Optical Society of America