{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T12:23:38Z","timestamp":1770726218545,"version":"3.49.0"},"reference-count":50,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2020,5,25]],"date-time":"2020-05-25T00:00:00Z","timestamp":1590364800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The terahertz spectrum provides tremendous opportunities for broadband gas-phase spectroscopy, as numerous molecules exhibit strong fundamental resonances in the THz frequency range. However, cutting-edge THz gas-phase spectrometer require cumbersome multi-pass gas cells to reach sufficient sensitivity for trace level gas detection. Here, we report on the first demonstration of a THz gas-phase spectrometer using a sub-wavelength thick ultrahigh-Q THz disc microresonator. Leveraging the microresonator\u2019s ultrahigh quality factor in excess of 120,000 as well as the intrinsically large evanescent field, allows for the implementation of a very compact spectrometer without the need for complex multi-pass gas cells. Water vapour concentrations as low as 4 parts per million at atmospheric conditions have been readily detected in proof-of-concept experiments.<\/jats:p>","DOI":"10.3390\/s20103005","type":"journal-article","created":{"date-parts":[[2020,5,26]],"date-time":"2020-05-26T03:29:10Z","timestamp":1590463750000},"page":"3005","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["Terahertz Gas-Phase Spectroscopy Using a Sub-Wavelength Thick Ultrahigh-Q Microresonator"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9091-5527","authenticated-orcid":false,"given":"Dominik Walter","family":"Vogt","sequence":"first","affiliation":[{"name":"Department of Physics, The University of Auckland, Auckland 1010, New Zealand"},{"name":"The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin 9016, New Zealand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3728-1016","authenticated-orcid":false,"given":"Angus Harvey","family":"Jones","sequence":"additional","affiliation":[{"name":"Department of Physics, The University of Auckland, Auckland 1010, New Zealand"},{"name":"The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin 9016, New Zealand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6324-4705","authenticated-orcid":false,"given":"Rainer","family":"Leonhardt","sequence":"additional","affiliation":[{"name":"Department of Physics, The University of Auckland, Auckland 1010, New Zealand"},{"name":"The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin 9016, New Zealand"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,5,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1038\/nphoton.2007.3","article-title":"Cutting-edge terahertz technology","volume":"1","author":"Tonouchi","year":"2007","journal-title":"Nat. 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