High-Q Fano resonances in diamond nanopillars

We report on the optical behaviour of a nanostructured diamond surface on a glass substrate. The numerical model reveals that a simple geometrical pattern sustains Fano-like resonances with a Q-factor as high as 3.5 · 105 that can be excited by plane waves impinging normally on the surface. We show that the geometrical parameters of the nanopillars affect both the resonant frequency and the line shape. The nanostructured surface can be straightforwardly used as a refractive index sensor with high sensitivity and linearity. Our findings show that diamond-based meta-surfaces are a valuable nanophotonic platform to control light propagation at the nanoscale, enabling large field enhancement within the nanoresonators that can foster both linear and nonlinear effects.