Alignment-insensitive bilayer THz metasurface absorbers exceeding 100% bandwidth

Kenney, Mitchell; Grant, James; Cumming, David R. S.

Abstract

Metamaterial absorbers have been a topic of considerable interest in recent years, with a particular focus on Terahertz (THz) frequencies due to many natural materials having a weak interaction with THz light. Great efforts have aimed to expand such THz absorbers to cover a wide bandwidth whilst also being highly efficient. However, many of these require cascaded or stacked multilayer resonant elements, where even a small deviation in the alignment between layers is extremely detrimental to the performance. Here, we propose a bilayer metasurface absorber (thickness ∼ λ/6) that is immune to such layer misalignments capable of exceeding a fractional bandwidth (FWHM) of 100% of the central frequency. The design works due to a novel absorption mechanism based on Salisbury Screen and anti-reflection absorption mechanisms, using fractal cross absorbers to expand the bandwidth. Our work is of particular benefit to developing devices which require ultra-wide bandwidth, such as bolometric sensing and planar blackbody absorbers, with the extremely robust absorption responses being unaffected by any misalignments between layers – a limiting factor of previous absorbers.

Citation

Kenney, M., Grant, J., & Cumming, D. R. S. (2019). Alignment-insensitive bilayer THz metasurface absorbers exceeding 100% bandwidth. Optics Express, 27(15), 20886-20900. https://doi.org/10.1364/oe.27.020886

• Journal Article Type: Article
• Acceptance Date: Jun 14, 2019
• Online Publication Date: Jul 11, 2019
• Publication Date: Jul 22, 2019
• Deposit Date: Sep 23, 2020
• Publicly Available Date: Sep 23, 2020
• Journal: Optics Express
• Electronic ISSN: 1094-4087
• Publisher: Optical Society of America
• Peer Reviewed: Peer Reviewed
• Volume: 27
• Issue: 15
• Pages: 20886-20900
• DOI: https://doi.org/10.1364/oe.27.020886
• Keywords: Atomic and Molecular Physics, and Optics
• Public URL: https://nottingham-repository.worktribe.com/output/4913396
• Publisher URL: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-15-20886
• Additional Information: Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.