Single-layer Planar Metasurface Lens with >170° Field of View

Abstract

Wide-angle optical functionality is crucial for implementation of advanced imaging and image projection devices. Conventionally, wide-angle operation is attained with complicated assembly of multiple optical elements. Recent advances in nanophotonics have led to metasurface lenses or metalenses, a new class of ultra-thin planar lenses utilizing subwavelength nanoantennas to gain full control of the phase, amplitude, and/or polarization of light. Here we present a novel metalens design capable of performing diffraction-limited focusing and imaging over an unprecedented > 170 angular field of view (FOV). The lens is monolithically integrated on a onepiece flat substrate and involves only a single layer of metasurface that corrects third-order Seidel aberrations including coma, astigmatism, and field curvature. The metalens further features a planar focal plane, which enables considerably simplified system architectures for applications in imaging and projection. We fabricated the metalens using Huygens meta-atoms operating at 5.2 m wavelength and experimentally demonstrated aberration-free focusing and imaging over the entire FOV. The design concept is generic and can be readily adapted to different meta-atom geometries and wavelength ranges to meet diverse application demands. Wide-angle metalenses: state-of-the-artWide-angle optical systems are vital to high performance imaging, detection, image or beam projection, and Fourier optics, among many other applications 1-4 . One of the earliest examples of such systems is the panoramic camera pioneered by Thomas Sutton in the year 1858, which consisted of a single water-filled spherical lens producing an image on a curved glass plate covered with reactive emulsion. Due to apparent difficulties in fabrication and handling of curved plates, the original approach was soon abandoned but it outlines the fundamental challenges associated with achieving wide-FOV imaging. Since then panoramic photography has been evolving along the path of planar detector planes while relying on compound lens assemblies, commonly known as "fisheye lenses", to reduce optical aberrations at large field angles. Such multi-lens architecture, however, increases the size, weight, and assembly complexity of optical systems.Metasurfaces, devices capable of controlling the phase and amplitude of propagating light with arrays of subwavelength structures, present a promising solution enabling flat and compact optical

Wide field-of-view metalens: a tutorial

“…This limitation can be overcome by replacing the air gap with a solid substrate. Shalaginov et al 40 , 52 . applied this approach to significantly expand the FOV of metalenses, demonstrating a flat fisheye lens with record >170-deg diffraction-limited FOV based on Huygens’ surface in the mid-IR 53 , 54 (Fig.…”

“…The last condition, r=h, corresponds to the image-space telecentric configuration, and thus Eq. (6) explains why all designs of this type in the literature 40 , 51 , 52 , 55 – 58 assume approximate telecentricity. The near-telecentric configuration implies that these WFOV lenses exhibit barrel distortion at large AOIs, which is evident from the experimental images presented in Fig.…”

Design for quality: reconfigurable flat optics based on active metasurfaces

“…The promise of metasurface optics lies in the arbitrary control of electromagnetic waves with an optically thin form factor that cannot be obtained by traditional bulk optics. Passive metasurfaces have successfully demonstrated important spherical, chromatic, and angle-dependent aberration correction capabilities [9][10][11][12][13][14][15][16][17][18]. Integrated with active components, the flat, pixelated metasurface architecture further facilitates the local and global tuning of their optical responses.…”

Neural Nano-Optics for High-quality Thin Lens Imaging

“…Metasurfaces also exhibit strong geometric aberrations that have limited their utility for wide field of view (FOV) imaging. Approaches that support wide FOV typically rely on either small input apertures that limit light collection 23 or use multiple metasurfaces 10 , which drastically increases fabrication complexity. Moreover, these multiple metasurfaces are separated by a gap that scales linearly with the aperture, thus obviating the size benefit of meta-optics as the aperture increases.…”