A Highly Efficient Bifunctional Dielectric Metasurface Enabling Polarization‐Tuned Focusing and Deflection for Visible Light

Abstract

A multifunctional metasurface has attracted drastically growing interest, serving as a prominent candidate to cope with both device miniaturization and integration. Conventional transmissive bifunctional metasurfaces working for visible light inherently suffer from several demerits owing to the use of geometric phase and spatial multiplexing scheme. Research endeavors have been mainly devoted to the implementation of a static device. In this work, a highly efficient bifunctional dielectric metasurface, taking advantage of a unit cell (UC) the building block of which capitalizes on a nanopost in hydrogenated amorphous silicon, is proposed and experimentally demonstrated to successfully enable polarization-mediated anomalous beam deflection and focusing in the visible band. Through the tailoring of the UC periodicity, we are capable of efficiently tuning the beam deflection angle and focusing distance. For the fabricated sample, the normal transverse-electric incidence within a spectral band from 600 nm to 715 nm is angle-resolved to a single diffraction order via the beam deflection, while a bright line focus is attained at the target focal plane for the normal transverse-magnetic incidence at  = 650 nm. This work will initiate a positive prospect for the development of highperformance tunable multifunctional metasurfaces.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Recent Advances in Polarization‐Encoded Optical Metasurfaces

“…Gao et al proposed and demonstrated a highly efficient bifunctional dielectric metasurface, whose building block capitalizes on anisotropic nanoposts made up of hydrogenated amorphous Si, as shown in Figure a. [ 82 ] Therefore, visible polarization‐encoded focusing and anomalous beam‐steering were implemented. By tailoring the unit cell's periodicity, the angle of beam deflection and distance of focusing can be effectively tuned.…”

Recent Progress on Ultrathin Metalenses for Flat Optics

“…The relative local phase and phase gradient can be calculated using the measured positions of focuses in a sub-pixel. The polarization multifunctionality of the metalens can also provide various opportunities for multiplexing deflection and focusing (Gao et al, 2019a) and for multi-generation of an optical vortex (Wang et al, 2020b). In addition to multifunctionality of polarization and frequency, angle multifunctional metalens gives miniaturized and powerful tools to quantitative phase imaging.…”

Design and Numerical Analysis of an Infrared Cassegrain Telescope Based on Reflective Metasurfaces

“…Being flat and ultrathin, metasurfaces can effectively reduce the size and weight of many optical systems, attracting increasing research interest in recent years. Researchers have demonstrated a plethora of ultrathin and flat optical devices based on metasurfaces, including metalens [8,9], beam deflectors [10,11], meta-holograms [12,13], color filters [14,15], optical vortex generators [16,17], nonlinear [18,19] and even quantum [20,21] optical devices, etc. Among them, Li et al demonstrated for the first time a Cassegrain telescope based on two flat, ultrathin metasurfaces operating in the infrared wavelength range [22], opening up a new avenue to circumvent difficulties faced by reflective optics with curved surfaces.…”