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We obtain optical instabilities in all-optical bistable systems arising from competing cooperative pathways at low input light levels. In particular for three-level atomic systems in the lambda and V configuration interacting with two independent cavity modes, we identify the necessary conditions related to the incoherent pathways required to obtain instabilities. The instabilities arise when atomic states involved in the bistable transition are leaky and have substantial population, where the incoherent processes adversely affect the cooperative behavior of the atomic ensemble.

Optical bistability is used to control the dispersion and absorption experienced by weak probe laser due to lambda system. We drive the system to exhibit periodic instability at lower input light strengths, and we explore nearby regime to achieve periodic refractive index and absorption.

We present novel hysteretic behaviour of a three-level ladder atomic system exhibiting double-cavity optical bistability in the mean-field limit. The two fields coupling the atomic system experience feedback via two independent, unidirectional, single mode ring cavities and exhibit cooperative phenomena, simultaneously. The system displays a range of rich dynamical features varying from normal switching to self pulsing and a period-doubling route to chaos for both the fields. We focus our attention to a new hump like feature in the bistable curve arising purely due to cavity induced inversion, which eventually leads to negative hysteresis in the bistable response. This is probably the only all-optical bistable system that exhibits positive as well as negative bistable hysteresis in different input field intensity regimes. For both the fields, the switching times, the associated critical slowing down, the self-pulsing characteristics, and the chaotic behaviour can be controlled to a fair degree, moreover, all these effects occur at low input light levels., 5 Pages, 3 figures. Feedback is welcome