On the giant enhancement of light in plasmonic or all-dielectric gratings containing nano-voids

We report the possibility of generating tremendous light-field enhancements within shallow nano-trenches made in a high-index dielectric material because of resonant behaviors that are reminiscent of what we get with sub-wavelength plasmonic cavities. High quality factors are explained through a modal analysis which gives explicit design rules. The thin dielectric void gratings could be a relevant alternative to plasmon-based devices for chemical sensing, or could inspire novel efficient wavelength-selective photo-absorbers by taking poorly absorbing materials.