SELF-OSCILLATIONS OF A BISTABLE ELEMENT IN 2 COUPLED HYBRID RING RESONATORS

A CdS crystal showing thermally induced optical bistability is incorpo rated into two coupled hybrid ring resonators with different delay tim es. Both delay times are much longer than the relaxation time of the n onlinearity. The resulting self-oscillations are investigated both exp erimentally and theoretically. We find two different types of oscillat ion modes. If the crystal is on the lower branch of the bistability du ring the longer delay time, step like oscillations similar to the case of a single resonator occur. If the crystal is in the lower state onl y for the shorter delay time (also the shorter of the two delay times is much longer than the relaxation time) we find more complicated mode s with plateaus and stairs because the long resonator acts as a memory for the system state before the switching process. We find complex mo de locking structures exhibiting farey-tree like transitions between d ifferent oscillation modes as well as mode coexistence. Based on an ad iabatic theory we compute the regions of existence of the different os cillation modes and compare them with experimental results.