Intensity-dependent Guided Wave Phenomena

The nonlinear mixing of optical beams has led to a rich spectrum of phenomena since the inception of the field in the early 1960's. This includes the generation of new frequencies, a host of nonlinear spectroscopies, and a variety of signal processing operations such as phase conjugation, optical bistability, and optical switching. In general, nonlinear optical interactions occur whenever the optical fields associated with one or more laser beams propagating in a material are large enough to produce polarization fields proportional to the product of two or more of the incident fields.' These nonlinear polarization fields radiate fields at the nonlinear frequency, which grows linearly with propagation distance under optimum conditions of phase matching. Hence the key to obtaining efficient nonlinear optical interactions is to maintain high optical intensities over the longest distance possible.