title: Subwavelength-thick lenses with high numerical apertures and large efficiency based on high-contrast transmitarrays.
abstract: Flat optical devices thinner than a wavelength promise to replace conventional free-space components for wavefront and polarization control. Transmissive flat lenses are particularly interesting for applications in imaging and on-chip optoelectronic integration. Several designs based on plasmonic metasurfaces, high-contrast transmitarrays and gratings have been recently implemented but have not provided a performance comparable to conventional curved lenses. Here we report polarization-insensitive, micron-thick, high-contrast transmitarray micro-lenses with focal spots as small as 0.57 λ. The measured focusing efficiency is up to 82%. A rigorous method for ultrathin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The micro-lenses, composed of silicon nano-posts on glass, are fabricated in one lithographic step that could be performed with high-throughput photo or nanoimprint lithography, thus enabling widespread adoption.
authors.affiliation: T. J. Watson Laboratory of Applied Physics, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, USA.
authors.forename: Amir
authors.identifier: http://orcid.org/0000-0001-8831-7552
authors.initials: A
authors.lastname: Arbabi
authors.affiliation: T. J. Watson Laboratory of Applied Physics, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, USA.
authors.forename: Yu
authors.identifier: http://orcid.org/0000-0001-7083-1270
authors.initials: Y
authors.lastname: Horie
authors.affiliation: T. J. Watson Laboratory of Applied Physics, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, USA.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Ball
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA.
authors.forename: Mahmood
authors.initials: M
authors.lastname: Bagheri
authors.affiliation: T. J. Watson Laboratory of Applied Physics, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, USA.
authors.forename: Andrei
authors.initials: A
authors.lastname: Faraon