Four-phase patterns in a forced nonlinear optical oscillator

We present preliminary theoretical and experimental results indicating that a high Fresnel number nonlinear optical oscillator with planar mirrors can display four-phase multistability, eventually leading to four-phase patterns. Such situation is similar to that emerging in extended oscillatory systems forced within a 4:1 resonance and, to the best of our knowledge, has not been predicted nor observed previously in an optical system. The fact that rocking (the forcing of a nonlinear oscillator around its natural frequency -1:1 resonance- with an amplitude modulated periodic signal) is able to transform phase invariant systems into phase bistable ones suggests that a similar forcing, applied now to an already phase bistable system, could lead to four-phase multistability. Here we explore such possibility both theoretically and experimentally.