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Resonant gas sensing in the terahertz spectral range using two-wire phase-shifted waveguide Bragg gratings

Yang Cao, Kathirvel Nallappan, Guofu Xu and Maksim A. Skorobogatiy

Article (2023)

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The development of low-cost sensing devices with high compactness, flexibility, and robustness is of significance for practical applications of optical gas sensing. In this work, we propose a waveguide-based resonant gas sensor operating in the terahertz frequency band. It features micro-encapsulated two-wire plasmonic waveguides and a phase-shifted waveguide Bragg grating (WBG). The modular semi-sealed structure ensures the controllable and efficient interaction between terahertz radiation and gaseous analytes of small quantities. WBG built by superimposing periodical features on one wire shows high reflection and a low transmission coefficient within the grating stopband. Phase-shifted grating is developed by inserting a Fabry–Perot cavity in the form of a straight waveguide section inside the uniform gratings. Its spectral response is optimized for sensing by tailoring the cavity length and the number of grating periods. Gas sensor operating around 140 GHz, featuring a sensitivity of 144 GHz/RIU to the variation in the gas refractive index, with resolution of 7 X 10 -5 RIU, is developed. In proof-of-concept experiments, gas sensing was demonstrated by monitoring the real-time spectral response of the phase-shifted grating to glycerol vapor flowing through its sealed cavity. We believe that the phase-shifted grating-based terahertz resonant gas sensor can open new opportunities in the monitoring of gaseous analytes.

Uncontrolled Keywords

terahertz technology; gas sensing; plasmonic waveguide; phase-shifted grating; additive manufacturing

Department: Department of Engineering Physics
Funders: National Natural Science Foundation of China
Grant number: 62205100
PolyPublie URL: https://publications.polymtl.ca/56750/
Journal Title: Sensors (vol. 23, no. 20)
Publisher: Multidisciplinary Digital Publishing Institute
DOI: 10.3390/s23208527
Official URL: https://doi.org/10.3390/s23208527
Date Deposited: 23 Jan 2024 12:29
Last Modified: 07 Apr 2024 01:09
Cite in APA 7: Cao, Y., Nallappan, K., Xu, G., & Skorobogatiy, M. A. (2023). Resonant gas sensing in the terahertz spectral range using two-wire phase-shifted waveguide Bragg gratings. Sensors, 23(20), 8527 (10 pages). https://doi.org/10.3390/s23208527


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