Terahertz Metagrating Accordion for Dynamic Beam Steering. Issue 11 (6th April 2022)

• Record Type: Journal Article
• Authors: Cheng, Jierong; Dong, Xipu; Chen, Sai; Yuan, Yiwu; Wen, Qiye; Chang, Shengjiang
• Is Part Of: Advanced optical materials. Volume 10:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-06
• Subjects: angle‐adaptive retroreflection -- beam steering -- dynamic beam steering -- metagratings -- terahertz; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.202200008
• Languages: English
• ISSNs: 2195-1071

Abstract

Abstract: Metasurfaces can be used to manipulate the beam direction beyond the Snell's law by the constitutive gradient elements. Independent control of the phase response of each element is usually required for real‐time beam steering, which is very challenging at terahertz (THz) frequencies. Here a type of accordion‐shaped single‐element metagratings for THz beam scanning and angle‐adaptive retroreflection is proposed. The metagrating is carefully designed to enhance the +1st order diffraction while suppressing other orders for efficient beam steering. Benefiting from the periodic arrangement, dynamic beam steering is realized by imparting desired momentum via mechanical compression and rotation, instead of the complicated element‐by‐element modulation. Beam scanning in a plane and over the 3D space is experimentally validated with elevation angles from 45° to 75° and azimuthal angles over 360°. An angle‐adaptive retroreflector by adding a metallic plate to the metagrating is studied with near perfect theoretical diffraction efficiency for incident angles within 40°–85°. The physical mechanism of wide‐angle high efficiency is detailed by the mode analysis, and can be generalized into other frequencies. The study here may find applications in THz communications and radar detections, and open a new avenue to facilitate reconfigurable metadevices for wavefront modulation. Abstract : Metasurfaces change the beam direction by a set of gradient elements. Independent control of each element is required for dynamic beam steering, which is challenging at terahertz frequencies. Here accordion‐shaped metagratings made of uniform elements are demonstrated for efficient beam steering and angle‐adaptive retroreflection at 0.14 THz through compression and rotation. The physical mechanism can be generalized to other frequencies.