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Passive Detection and Imaging of Human Body Radiation Using an Uncooled Field-Effect Transistor-Based THz Detector

D. Cibiraite-Lukenskiene1, K. Ikamas2,3, T. Lisauskas4, V. Krozer1,5, H.G. Roskos1 and A. Lisauskas1,2,6

Published in:

Sensors, vol. 20, no. 15, art. 4087, doi:10.3390/s20154087 (2020).


This work presents, to our knowledge, the first completely passive imaging with human-body-emitted radiation in the lower THz frequency range using a broadband uncooled detector. The sensor consists of a Si CMOS field-effect transistor with an integrated log-spiral THz antenna. This THz sensor was measured to exhibit a rather flat responsivity over the 0.1-1.5-THz frequency range, with values of the optical responsivity and noise-equivalent power of around 40 mA/W and 42 pW/√Hz, respectively. These values are in good agreement with simulations which suggest an even broader flat responsivity range exceeding 2.0 THz. The successful imaging demonstrates the impressive thermal sensitivity which can be achieved with such a sensor. Recording of a 2.3 × 7.5-cm2-sized image of the fingers of a hand with a pixel size of 1 mm2 at a scanning speed of 1 mm/s leads to a signal-to-noise ratio of 2 and a noise-equivalent temperature difference of 4.4 K. This approach shows a new sensing approach with field-effect transistors as THz detectors which are usually used for active THz detection.

1 Physikalisches Institut, J.W. Goethe University Frankfurt, 60438 Frankfurt, Germany
2 Institute of Applied Electrodynamics and Telecommunications, Vilnius University, 10257 Vilnius, Lithuania
3 The General Jonas Zemaitis Military Academy of Lithuania, 10322 Vilnius, Lithuania
4 MB "Terahertz Technologies", 01116 Vilnius, Lithuania
5 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH), 12489 Berlin, Germany
6 CENTERA Laboratories, Institute of High Pressure Physics PAS, 01-142 Warsaw, Poland


passive imaging; human-body radiation; THz detection; TeraFET; field-effect transistor; terahertz

Copyright © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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