Abstract

We discuss the properties of an optical circuit with gain and loss provided by two-beam coupling in a photorefractive medium and with a photorefractive element as a programmable mirror to provide feedback. As with an ordinary ring resonator having photorefractive gain and loss the circuit can exhibit reversible or irreversible bistability and self-pulsing. In the limit that the feedback element has a response that is slow compared to the gain and loss, its behavior is much like the conventional case. However, whereas a conventional ring resonator has a well-defined detuning characteristic dependent on the round trip length, in the present circuit a fast photorefractive element continually compensates for changes in the round trip path length. The bistability and self-pulsing characteristics are strongly affected by the relative time constants of the three photorefractive media and by the relative magnitudes of the small signal gain and loss. In particular, the on state of the ring has a memory time determined by the time constant of the feedback element.

© 1989 Optical Society of America