Intrinsic optical bistability via switching between saturable and reverse saturable absorption.

We present a novel approach to achieving intrinsic optical bistability and multistability through the interplay between saturable and reverse saturable absorption. Our findings reveal that the stable points on the optical bistability curve align with the switching points of intensity-dependent nonlinear absorption. By analyzing the optical properties of a four-level cascade quantum system, we demonstrate that these switching behaviors can be triggered by applying laser fields to induce nonlinear absorption. Furthermore, we propose a comprehensive model to describe the intensity-dependent nonlinear absorption within this quantum system. Finally, it is shown that the optical bistability switches to the multistability when the detuning of applied fields exceeds the multi-photon resonance condition.