Critical coupling in Cavity Resonator Integrated Grating Filters (CRIGFs) for SHG control

Abstract

We demonstrate experimentally critical coupling for nonlinear conversion in grating-coupled Fabry-Pérot planar microcavities known as Cavity-Resonant Integrated Grating Filters (CRIGFs). Novel asymmetric designs offer Q-factors from 1000 to 7000 and allow critical coupling with maximised SHG. We developed an improved coupled-mode model for the linear and non-linear spectral response of CRIGFs which allows accurate insight on the intrinsic and coupling losses in these microcavities.