ALL-OPTICAL SWITCHING PROPERTY OF AN MQW-SANDWICH NONLINEAR DIRECTIONAL COUPLER WITH NONLINEAR LOSSES

We analyze all-optical switching property of a nonlinear directional c oupler (NLDC) having an MQW coupling layer with both nonlinear and lin ear losses, and examine the effect of nonlinear losses. We use the Gal erkin finite element method accompanied by a predictor-corrector algor ithm. The propagation loss along the strongly-coupled NLDC decreases w ith increasing nonlinear absorption coefficient due to saturation in a bsorption. A propagation loss of 8.18 dB or 2.38 dB in the bar state o r the cross state is much smaller than the bulk loss of MQW structure which exceeds 50 dB. The nonlinear losses lengthen the coupling length and bring it close to that of a lossfree NLDC, while the linear losse s shorten. It is found that the property of the cross state is greatly improved by counting the nonlinear losses: The cross-state output pow er and the output power ratio of two waveguides increase, and the cros s state input power, that is, the switching power decreases.