Second harmonic enhancement in a hybrid plasmonic-lithium niobate metasurface enabled by guided mode resonances [Invited]

We study the enhancement of second-harmonic generation (SHG) from a thin lithium niobate film on insulator covered with a gold nanoantenna array. The array is engineered to excite the TE0 guided mode of the thin film at the fundamental harmonic. By spectrally detuning the localized antenna resonance from the collective guided mode resonance, we achieve control over the resonance quality factor, which enhances the nonlinear interaction. Experimental measurements show a 22-fold enhancement of SHG compared to the bare thin film, an absolute conversion efficiency of 1.35 × 10−5, and an angular tunability of the guided mode resonance of ∼100 nm. The SHG efficiency and linewidth are consistent with the observed collective resonance properties, and are limited mostly by fabrication imperfections. These results emphasize the potential of hybrid plasmonic metasurface-waveguide configurations for integrated photonic applications.