Second-harmonic-generation enhancement in cavity resonator integrated grating filters

We demonstrate numerically and experimentally second-harmonic generation (SHG) in a cavity resonator integrated grating filter (CRIGF, a planar cavity resonator made of Bragg grating reflectors) around 1550 nm. SHG is modeled numerically for several different systems, including a thin plane layer of LiNbO₃ without and with a grating coupler to excite a waveguide mode. We demonstrate that when the waveguide mode is confined to a CRIGF, designed to work with focused incident beams, the SHG power is increased more than 30 times, compared to the case of a single grating coupler used with an almost collimated pump beam.