Jung, Hyunseung; Hale, Lucy L; Briscoe, Jayson; Sarma, Raktim; Luk, Ting Shan; Addamane, Sadhvikas J; Reno, John L; ... Mitrofanov, Oleg; + view all Jung, Hyunseung; Hale, Lucy L; Briscoe, Jayson; Sarma, Raktim; Luk, Ting Shan; Addamane, Sadhvikas J; Reno, John L; Brener, Igal; Mitrofanov, Oleg; - view fewer (2022) Terahertz Detection Using Enhanced Two-Step Absorption in Photoconductive Metasurfaces Gated at lambda=1.55 mu m. Advanced Optical Materials , Article 2201838. 10.1002/adom.202201838.

Text Revised Manuscript_AdOM_1550 nm GaAs MS_HJung_LH_preprint.pdf - Accepted Version Access restricted to UCL open access staff until 31 October 2023. Download (1MB)

Abstract

Superior ultrafast photoconductive properties make low temperature grown (LT) GaAs one of the best materials for photoconductive terahertz (THz) detection. However, the large bandgap of LT-GaAs limits its operation to gating at wavelengths shorter than 870 nm. Here, it is demonstrated for the first time that nanostructuring the LT-GaAs into a highly absorbing metasurface enables THz photoconductive detection with a pulsed laser at λ = 1.55 µm. The very weak sub-bandgap absorption mediated by midgap states in LT-GaAs is strongly enhanced using the concept of perfect absorption via degenerate critical coupling. Integrated with a THz antenna, the LT-GaAs metasurface enables high sensitivity THz detection with a high dynamic range of 60 dB and large bandwidth up to 4.5 THz. The LT-GaAs metasurface has the potential to serve as a universal ultrafast switching element for THz applications, enabling low-cost, turn-key THz systems for a variety of real-world applications.

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