Fig. 1.
Diamond immersion metalens. a Subwavelength pillars extending from the surface of a single-crystal diamond substrate are designed to create a high-numerical-aperture immersion lens for coupling nitrogen-vacancy (NV)-center photoluminescence to a collimated beam in air. Inset: Scanning electron microscope (SEM) image of fabricated metalens with closeup of etched diamond pillars. The scale bar corresponds to 1 μm. b Bloch-mode effective index, neff, and corresponding optical pathlength difference, ϕ, as a function of pillar diameter, d, at λ = 700 nm. This map is used to create the lens pattern shown in a