  Nano-resonator integrated with two-dimensional materials (e.g. transition
metal dichalcogenides) have recently emerged as a promising nano-optoelectronic
platform. Here we demonstrate resonatorenhanced second-harmonic generation
(SHG) in tungsten diselenide using a silicon photonic crystal cavity. By
pumping the device with the ultrafast laser pulses near the cavity mode at the
telecommunication wavelength, we observe a near visible SHG with a narrow
linewidth and near unity linear polarization, originated from the coupling of
the pump photon to the cavity mode. The observed SHG is enhanced by factor of
~200 compared to a bare monolayer on silicon. Our results imply the efficacy of
cavity integrated monolayer materials for nonlinear optics and the potential of
building a silicon-compatible second-order nonlinear integrated photonic
platform.
