Low-Contrast Dielectric Metasurface Optics

• Published in: ACS photonics Vol. 3; no. 2; pp. 209 - 214
• Main Authors: Zhan, Alan, Colburn, Shane, Trivedi, Rahul, Fryett, Taylor K, Dodson, Christopher M, Majumdar, Arka
• Format: Journal Article
• Language: English
• Published: American Chemical Society 17.02.2016
• Subjects: diffractive optics; silicon nitride photonics; dielectric metasurface; lens; vortex beam generator
• ISSN: 2330-4022; 2330-4022
• DOI: 10.1021/acsphotonics.5b00660

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.