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Near-field terahertz imaging using sub-wavelength apertures without cutoff

Liu, S; Mitrofanov, O; Nahata, A; (2016) Near-field terahertz imaging using sub-wavelength apertures without cutoff. Optics Express , 24 (3) pp. 2728-2736. 10.1364/OE.24.002728. Green open access

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Abstract

We demonstrate near-field imaging capabilities of a conical waveguide without cutoff using broadband terahertz (THz) radiation. In contrast to conventional conically tapered waveguides, which are characterized by strong suppression of transmission below the cutoff frequency, the proposed structure consists of two pieces, such that there is an adjustable gap along the length of the waveguide. We also ensure that the sidewalls are thin in the vicinity of the gap. The combination of these geometrical features allow for significantly enhanced transmission at frequencies below the cutoff frequency, without compromising the mode confinement and, consequently, the spatial resolution when used for imaging applications. We demonstrate near-field imaging with this probe simultaneously at several frequencies, corresponding to three regimes: above, near and below the cutoff frequency. We observe only mild degradation in the image quality as the frequency is reduced below the cutoff frequency. These results suggest that further refinements in the probe structure will allow for improved imaging capabilities at frequencies well below the cutoff frequency.

Type: Article
Title: Near-field terahertz imaging using sub-wavelength apertures without cutoff
Open access status: An open access version is available from UCL Discovery
DOI: 10.1364/OE.24.002728
Publisher version: http://dx.doi.org/10.1364/OE.24.002728
Language: English
Additional information: © 2016 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.
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/1505818
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