Mode interplay via quadratic cascading in a lithium niobate waveguide for all-optical processing

The effects of the nonlinear interplay between modes of a lithium niobate channel waveguide are numerically investigated. Based on the nonlinear phase-shift obtainable via up- and down-conversion of each mode at the input frequency into and from the second-harmonic modes generated through Type I and Type II interactions, the waveguide can operate as an all-optical transistor with large small-signal-gain, and as a mode-mixing device capable of spatial switching and routing. It exhibits good switching contrast at 1.55 mu m with low driving powers.