Enhanced Second-Harmonic\nGeneration in a Monolayer\nTungsten Diselenide Integrated Silicon Nitride Nanocavity

Observations of nonlinear optical\nphenomena are greatly\nhindered\nby the large optical power requirements. Nanophotonic cavities can\ndrastically reduce the required optical powers thanks to the strong\nspatial and temporal confinement of light. Furthermore, two-dimensional\natomically thin transition metal dichalcogenides boast high nonlinear\noptical coefficients and are promising candidates for hybrid nanophotonics\ndue to their ease of integration and compatibility with many substrates\nwithout requiring explicit lattice matching. Here, we demonstrate\ncavity enhanced second harmonic generation in a monolayer tungsten\ndiselenide integrated silicon nitride nanocavity. With a fundamental\nfrequency close to the excitonic resonance and a large second order\nsusceptibility at wavelengths near 800 nm, we observed a cavity enhancement\nof more than 3 orders of magnitude of second harmonic generation compared\nto bare monolayer.