Abstract

Photorefractive mode coupling between resonators provides a simple model for self-pumped phase conjugators,¹ in which instability may occur because of energy transfer among different oscillation modes inside the crystal. In this paper, we consider the coupling between two unidirectional ring resonators.² The first resonator is driven by an external laser beam by means of photorefractive two-wave mixing. The internal oscillating beam is then employed to drive the second ring resonator by the same mechanism. We find that with proper choice of resonator parameters, two type of oscillations may occur. In the first type the primary resonator, which is driven by the external laser, oscillates, but the secondary resonator, which is driven by the primary resonator, does not oscillate. In the second type the primary and secondary resonators oscillate simultaneously, and the oscillation of one resonator affects that of the other. We also find that even though the two resonators can oscillate separately, they may not perform steady-state oscillation when they are coupled. In this case the coupled system is not stable, which may result in temporal instability similar to that which occurs in self-pumped phase conjugators. Our results include the conditions for each of the above operation modes, the intensities and frequencies for steady-state oscillations, and the change of oscillation in one resonator that is brought about by detuning the other one.

© 1990 Optical Society of America