A multi-mode super-fano mechanism for enhanced third harmonic generation in silicon metasurfaces

We present strong enhancement of third harmonic generation in an amorphous silicon metasurface consisting of elliptical nano resonators by a new type of multi-mode Fano mechanism. Quantitative nonlinear measurements were performed, in which an absolute conversion efficiency as high as \(\eta_{max} = 2.8 \times 10^{-7}\) at a peak power intensity of \(1.2\;\text{GW}\,\text{cm}^{-2}\) and amplification factors of up to \(\sim900\) compared to an unpatterned silicon film are found