Optical Bistability Based on Self-Focusing

Two years ago, the first proposal and demonstration of self-focusing optical bistability was published.1 In this paper it was shown that a self-focused beam in a nonlinear medium would exhibit hysteresis if the beam were reflected back on itself. The effect was demonstrated using a dye laser beam and Na vapor as the nonlinear medium. The optical hysteresis observed is in good qualitative agreement with a recently - published analysis of this system.2 By taking account of the saturation of the nonlinearity, more complex behavior has been predicted.2 This behavior is due to oscillations of the spot size as the self-focused beam propagates through the nonlinear medium. In this paper we report on our experimental studies of optical multistability due to these spot size oscillations.