Abstract

For a laser passing through an optically thin nonlinear film, the transmission can be calculated by considering only the effect associated with the nonlinear intensity-dependent transverse phase shift. The radial intensity distribution at a distance from the nonlinear film can be calculated using Kirchhoff's integral and analytically studied as a function of several optical and material parameters. It is found that the intensity distribution may be classified in terms of the diffractive phase for positive or negative nonlinearities. Accordingly, the transmitted intensity distribution can take various forms, with e.g., intensified central region with interference rings, darkened central region, and alternatively bright and darkened central region, as the input intensity is increased. The on-axis intensity can also exhibit power-limiting behavior or unidirectional switching effects. These effects have been experimentally observed. In the case of a positive feedback (e.g., with a partially reflecting mirror downstream), optical bistability in the intensity distribution (at both on-axis and off-axis regions) arises. The conditions for observing optical bistability were found to be described in a rather consistent manner in terms of the diffractive phase mentioned above.

© 1986 Optical Society of America