Multistable all-optical switching behavior of the asymmetric nonlinear directional coupler

Abstract

Asymmetric dual core nonlinear directional couplers that include an increasing self phase modulation profile are examined. The asymmetry is associated with the self phase modulation profile of one of the channels (direct channel). Looking at the transmission characteristics of the device, through the direct channel, one observes that, when pumping in the direct channel, there is a decrease in the critical power which is lower compared with the symmetric coupler, and the critical power is a single-value function of the nonlinearity. For the pump power in the cross channel the transmission function of the coupler presents regions of multistability, where the coupler presents more than one critical power for certain values of the self phase modulation profile index. It was also observed that all the profiles under study, with increasing self phase modulation profile, present this behavior. For the studied profiles, one region of multistability was observed where three possible critical powers were observed. However, for the exponential profile, a second region was observed for a higher value of the self phase modulation profile parameter. It is concluded that to operate the asymmetric coupler in a single-value region for the critical power, the exponential self phase modulation profile presents the best behavior for the profiles under study.