Highly efficient second-harmonic generation of a reflective waveguide-coupled photonic nanocavity.

In order to enhance second-harmonic generation (SHG) efficiency in a waveguide-coupled photonic nanocavity, we introduce a reflector at the edge of the waveguide and investigate its influence on input power and SHG efficiency. SHG efficiency and critical input power of the reflective waveguide-coupled cavity are controlled by the reflection amplitude and phase delay of the reflector. At input powers considerably lower than the critical power, SHG efficiency increases by up to three orders of magnitude higher than the case without reflector. Moreover, SHG efficiency of 100% at critical input power, which is twice that of the previous result, can be achieved over a wide phase range. These results prove the feasibility and controllability of highly efficient nonlinear optical devices.