SIGNAL SWITCHING BY A CONTROL BEAM IN A NONLINEAR COUPLER

Power- and phase-controlled all-optical switching in a nonlinear fused -tapered coupler is presented. The induced switching is caused by a co ntrol beam applied to the coupler and is insensitive to the relative p hase variation between the control and the signal. The switching behav ior depends on the choice of the frequency of the control, its polariz ation, its strength, and the arm from which it is applied to the coupl er. Depending on these initial conditions, the critical switching powe r ranges from being reduced as compared with the no-control case to be ing increased and even being nonexistent. The underlying physical conc epts presented here can be generalized to include any two-mode-interfe rence coupler device.