All-optical logic gates based on wavelength conversion in a nonlinear directional coupler

In this paper, we theoretically investigate all-optical logic gates based on wavelength conversion in a nonlinear directional coupler. The switching of a weak continuous-wave (cw) light is controlled by two pump lights, as a result, the information on the pump light transfers to the cw light by controlling different combinations of the two pump lights. Firstly we study the switching characteristic of the device and select in a way to provide the best average values of Xratio. Finally we realize logic operations C=A⊕BC=A⊕B and D=A⊕B¯. The Xratio is higher than that of the ordinary methods and the all-optical logic gates based on wavelength conversion exhibit high switching contrast and have a better switching characteristic.