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Photoconductive Terahertz Near-Field Detector with a Hybrid Nanoantenna Array Cavity

Mitrofanov, O; Brener, I; Luk, TS; Reno, JL; (2015) Photoconductive Terahertz Near-Field Detector with a Hybrid Nanoantenna Array Cavity. ACS Phtonics , 2 (12) pp. 1763-1768. 10.1021/acsphotonics.5b00475. Green open access

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Abstract

anoscale structuring of optical materials leads to modification of their properties and can be used for improving efficiencies of photonic devices and for enabling new functionalities. In ultrafast optoelectronic switches for generation and detection of terahertz (THz) radiation, incorporation of nanostructures allows us to overcome inherent limitations of photoconductive materials. We propose and demonstrate a nanostructured photoconductive THz detector for sampling highly localized THz fields, down to the level of λ/150. The nanostructure that consists of an array of optical nanoantennas and a distributed Bragg reflector forms a hybrid cavity, which traps optical gate pulses within the photoconductive layer. The effect of photon trapping is observed as enhanced absorption at a designed wavelength. This optically thin photoconductive THz detector allows us to detect highly confined evanescent THz fields coupled through a deeply subwavelength aperture as small as 2 μm (λ/150 at 1 THz). By monolithically integrating the THz detector with apertures ranging from 2 to 5 μm we realize higher spatial resolution and higher sensitivity in aperture-type THz near-field microscopy and THz time-domain spectroscopy.

Type: Article
Title: Photoconductive Terahertz Near-Field Detector with a Hybrid Nanoantenna Array Cavity
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acsphotonics.5b00475
Publisher version: http://dx.doi.org/10.1021/acsphotonics.5b00475
Language: English
Additional information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Photonics, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acsphotonics.5b00475.
Keywords: nanoantenna, terahertz, near-field microscopy, light trapping, plasmons
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/1476120
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