  Manipulating light on the nanoscale has become a central challenge in
metadevices, resonant surfaces, nanoscale optical sensors, and many more, and
it is largely based on resonant light confinement in dispersive and lossy
metals and dielectrics. Here, we experimentally implement a novel strategy for
dielectric nanophotonics: Resonant subwavelength confinement of light in air.
We demonstrate that voids created in high-index dielectric host materials
support localized resonant modes with exceptional optical properties. Due to
the confinement in air, the modes do not suffer from the loss and dispersion of
the dielectric host medium. We experimentally realize these resonant Mie voids
by focused ion beam milling into bulk silicon wafers and experimentally
demonstrate resonant light confinement down to the UV spectral range at 265 nm
(4.68 eV). Furthermore, we utilize the bright, intense, and naturalistic
colours for nanoscale colour printing. The combination of resonant dielectric
Mie voids with dielectric nanoparticles will more than double the parameter
space for the future design of metasurfaces and other micro- and nanoscale
optical elements and push their operation into the blue and UV spectral range.
In particular, this extension will enable novel antenna and structure designs
which benefit from the full access to the modal field inside the void as well
as the nearly free choice of the high-index material.
