Abstract: Systems and methods are described herein for manufacturing high-index, low-absorption materials for use in visible light optical metasurfaces. Methods of manufacturing or forming hydrogenated amorphous silicon (a-Si:H), silicon-rich nitride (SRN), and hydrogenated silicon-rich nitride (SRN:H) are described herein that exhibit high indices of refraction and low extinction coefficients for visible wavelengths of optical radiation. Optical metasurfaces, including optical metalenses and waveguide couplers, are described herein that utilize the a-Si:H, SRN, and/or SRN:H materials.

Abstract: According to various embodiments, a device may include a light-emitting diode (LED) to generate optical radiation at an operational wavelength with a divergent emission profile, such as a Lambertian emission profile, relative to a planar face thereof. A metalens may be positioned to modify the divergent emission profile of the optical radiation from the LED to have a modified transmission profile. The metalens may comprise, for example, a substrate and a two-dimensional array of passive pillars that extend from the substrate with a radially symmetric pattern of varying pillar diameters. The pillars may be spaced from one another according to a uniform subwavelength interelement spacing. The diameters of the pillars are selected as a function of the operational wavelength to provide a target phase gradient that modifies the divergent emission profile of the optical radiation from the LED to have the modified transmission profile.