EFFECT OF LAYER-THICKNESS RANDOMNESS ON GAP SOLITONS AND OPTICAL BISTABILITY IN NONLINEAR SUPERLATTICES WITH PHOTONIC STOP GAPS

We calculate the nonlinear optical response of finite random-thickness superlattices and investigate the effect of randomness on gap soliton s and optical bistability. The structures we consider are composed by alternating stacking of linear and nonlinear layers with randomly dist ributed thicknesses. We calculate the transmissivity for superlattices with a different extent of randomness by numerically solving the nonl inear wave equation. The frequency of incident light is within a stop gap that is produced by the modulation of the linear part of the diele ctric constant. We find that for samples with different degree of rand omness the bistability still exists, but the peaks of the transmission resonance caused by the nonlinearity are lowered and shifted towards the direction of high incident power. More multivalued branches of tra nsmissivity, as a function of the incident power, emerge in some regio ns when randomness is introduced. The excitations of the gap solitons that are responsible for the resonance in the transmissivity are also suppressed by the randomness.