DYNAMIC CONTROL OF THE SPATIAL MODES IN THE EXTERNAL RESONATOR OF A SEMILINEAR PHASE-CONJUGATE MIRROR

We describe a technique that causes the radiation within the external resonator of a self-starting, semilinear phase-conjugate mirror to col lapse into a single spatial mode. We have developed a model based on c ompetition between gratings in one interaction volume to explain the o bserved dynamic behavior. The model shows that, once the system reache s the steady state, two gratings, whose amplitudes vary throughout spa ce in proportion to each other, form. As a result, we can obtain analy tic solutions for the steady state by using an interpretation of four- wave mixing in terms of two-wave mixing. This interpretation can be us ed in both the transmission and the reflection geometries for real or complex coupling with no absorption.