Twin core nonlinear couplers with gain and loss

Twin core nonlinear couplers that include gain and loss are examined. Of the various structures (ranging from couplers composed of two active cores and two lossy cores to those composed of one active or lossy core and one conventional core) considered, the most interesting case is the coupler composed of one core with a certain amount of gain and the other core with an equal amount of loss where ideal low power switching is possible in a comparatively short coupler. The presence of gain in one core is found to be responsible for reduction in switching power and/or shortening in the device length, while the introduction of the loss in the other core plays the role of idealizing switching. A physical model is also presented to explain the demonstrated merits based on the operation of linear couplers with gain and loss