LOSS AND NONLINEARITY SATURATION EFFECTS ON THE BISTABILITY OF NONLINEAR DISTRIBUTED-FEEDBACK STRUCTURES

We investigate theoretically the effects of optical absorption and sat uration of the nonlinear index of refraction on the bistability of non -linear distributed feedback structures (NLDFBs). By assuming that the Kerr non-linearity saturates in an exponential fashion, we obtain for the first time closed-form expressions for the so-called self-phase a nd cross-phase modulation terms. Our investigation shows that both abs orption and, in particular, saturation significantly affect the bistab le properties of this structure and in many cases eliminate this respo nse completely. In some cases, however, saturation alters the NLDFB's transfer characteristics in a potentially useful manner. We find that weak levels of saturation may increase the contrast ratio between the intensities of the high and low bistable states. At increasing levels of saturation, where bistability is no longer observed, we find regime s where the NLDFB structure could possibly be used for optical amplifi cation.