Varifocal Metalens Using Tunable and Ultralow‐loss Dielectrics. Issue 6 (3rd January 2023)

• Record Type: Journal Article
• Authors: Wang, Mengyun; Lee, June Sang; Aggarwal, Samarth; Farmakidis, Nikolaos; He, Yuhan; Cheng, Tangsheng; Bhaskaran, Harish
• Is Part Of: Advanced science. Volume 10:Issue 6(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-03
• Subjects: near‐IR wavelengths -- Sb2Se3 -- tunable metalens -- ultralow‐loss phase‐change materials; Science -- Periodicals; 505
• DOI: 10.1002/advs.202204899
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: The field of flat optics that uses nanostructured, so‐called metasurfaces, has seen remarkable progress over the last decade. Chalcogenide phase‐change materials (PCMs) offer a promising platform for realizing reconfigurable metasurfaces, as their optical properties can be reversibly tuned. Yet, demonstrations of phase‐change metalenses to date have employed material compositions such as Ge2 Sb2 Te5, which show high absorption in the visible to near‐IR wavelengths particularly in their crystalline state, limiting the applicability. Here, by using a low‐loss PCM Sb2 Se3, for the first time, active polarization‐insensitive phase‐change metalenses at near‐IR wavelengths with comparable efficiencies in both material states are shown. An active metalens with a tunable focusing intensity of 95% and a focusing efficiency of 23% is demonstrated. A varifocal metalens is then demonstrated with a tunable focal length from 41 to 123 µm with comparable focusing efficiency (5.7% and 3%). The ultralow‐loss nature of the material introduces exciting new possibilities for optical communications, multi‐depth imaging, beam steering, optical routing, and holography. Abstract : Sb2 Se3 is a remarkable, highly efficient ( κ = 0), and tunable (∆ n = 0.75) dielectric material at near‐IR wavelengths. This ultralow‐loss material is utilized to realize reconfigurable metalenses at near‐IR. Taking advantage of the low‐loss nature of the material, both single focal metalens with tunable focusing intensity as well as varifocal metalens with comparable efficiencies are demonstrated.