Autowaves in two-wave mixing in photorefractive media

The phase part of the system of equations describing two-wave mixing in a photorefractive strongly inertial medium is studied analytically and numerically. It is shown that the solution of the system of equations evolves through a series of quasi-stationary states, and the system switches between them due to a nonlinear wave. The velocity and profile of such a "switching wave" are completely determined by these states, which is an indication of an autowave process. The results show that the development of four-wave mixing in a strongly illuminated photorefractive medium is inevitably accompanied by intensity fluctuations.