1 research outputs found
Low-Contrast Dielectric Metasurface Optics
The miniaturization of current image
sensors is largely limited
by the volume of the optical elements. Using a subwavelength-patterned
quasi-periodic structure, also known as a metasurface, one can build
planar optical elements based on the principle of diffraction. Recent
demonstrations of high-quality metasurface optical elements are mostly
based on high-refractive-index materials. Here, we present a design
of low-contrast metasurface-based optical elements. We fabricate and
experimentally characterize several silicon nitride-based lenses and
vortex beam generators. The fabricated lenses achieved beam spots
of less than 1 μm with numerical apertures as high as ∼0.75.
We observed a transmission efficiency of 90% and focusing efficiency
of 40% in the visible regime. Our results pave the way toward building
low-loss metasurface-based optical elements at visible frequencies
using low-contrast materials and extend the range of prospective material
systems for metasurface optics