Abstract: An optical device includes a substrate, a reflective layer disposed over the substrate, and a metalens disposed over the reflective layer. The metalens includes a plurality of nanopillars, the plurality of nanopillars together specifying a phase profile such that the metalens has a focal length that is substantially constant over a wavelength range of an incident light of about 490 nm to about 550 nm.

Abstract: A phase shift element includes a substrate and a dielectric ridge waveguide (DRW) disposed on the substrate. The DRW includes a dielectric material, and a width of the DRW is less than 500 nanometers (nm). A meta-grating includes a substrate and multiple dielectric ridge wave-guides (DRWs) disposed on the substrate.

Abstract: A colorimetric sensor including: a substrate; and a periodic array of nanostructures provided to the substrate, wherein the periodic array of nanostructures is configured to provide a change in color based on a medium being within a predetermined distance of the colorimetric sensor. The periodic array of nanostructures may be configured (width, height, spacing) to provide optical wave-guide properties or surface Plasmon resonance in order to effect a distinct change in color based on the medium being sensed. In some cases, the colorimetric may include a reflective surface to reflect light from the sensor. Further, the reflective surface may be metallic.