Unstable Phase-Conjugate Resonator

A fundamental Gaussian mode in a phase-conjugate resonator consisting of conventional optical elements and a phase-conjugate mirror constructed by means of degenerate four-wave mixing is analyzed. A ray matrix method is used for the analysis by taking the finite radii of wavefront curvature and the finite beam radii of pump waves into account. It is suggested that the phase-conjugate resonator is generally an unstable resonator.