Optical bistability derived from the negative nonlinear absorption effect in erbium doped materials

Optical bistability derived from the negative nonlinear absorption effect was investigated in erbium-doped garnet crystals, glasses and semiconductors using a 1.53 μm laser diode. The optical bistability was observed in a laser intensity range of the order of mW cm−2. The transmitted laser intensity, propagating through the sample, decreased exponentially by the familiar exponential law. However, the amplitude of the optical bistability increased logarithmically as the sample length was increased. The amplitude decreased exponentially when the incident laser intensity was decreased. The optical bistability can be explained by considering an enhanced absorption for a multi-level system of the erbium ion.