We demonstrate double-resonantly enhanced SH harmonic generation at 402 ± 0.5 nm of encapsulated WS 2 -flakes, as shown in Figure 1b+c, pumped at 805 ± 1 nm, including quadratic energy dependency and polarization dependency and discuss possible generalization schemes. The resonator is implemented as a monolithic element composed of a pair of DBRs and a dielectric spacer, which contains a layer of monolayer crystals.

Transition metal dichalcogenides (TMDCs) are semiconducting 2D-materials with a direct bandgap in a range of 1.0 to 2.5 eV [1] . They exhibit strong second-order nonlinearity per unit thickness, making them interesting for nonlinear light-conversion devices [2] . Due to their small thickness, an interaction enhancement is paramount for efficient operation [3] . We have previously demonstrated that such enhancement can be acchieved by embedding TMDCs into monolithic resonators [4] if a gentle coating process compliant with the sensitive nature of the monolayer TMDC flakes is utilized.