{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T15:36:12Z","timestamp":1778686572053,"version":"3.51.4"},"reference-count":52,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2020,5,15]],"date-time":"2020-05-15T00:00:00Z","timestamp":1589500800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Natural Sciences and Engineering Research Council of Canada","doi-asserted-by":"publisher","award":["N\/A"],"award-info":[{"award-number":["N\/A"]}],"id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Korea Carbon Capture and Sequestration R&amp;D Center","award":["N\/A"],"award-info":[{"award-number":["N\/A"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A novel and compact interferometric refractive index (RI) point sensor is developed using hollow-core photonic crystal fiber (HC-PCF) and experimentally demonstrated for high sensitivity detection and measurement of pure gases. To construct the device, the sensing element fiber (HC-PCF) was placed between two single-mode fibers with airgaps at each side. Great measurement repeatability was shown in the cyclic test for the detection of various gases. The RI sensitivity of 4629 nm\/RIU was demonstrated in the RI range of 1.0000347\u20131.000436 for the sensor with an HC-PCF length of 3.3 mm. The sensitivity of the proposed Mach\u2013Zehnder interferometer (MZI) sensor increases when the length of the sensing element decreases. It is shown that response and recovery times of the proposed sensor inversely change with the length of HC-PCF. Besides, spatial frequency analysis for a wide range of air-gaps revealed information on the number and power distribution of modes. It is shown that the power is mainly carried by two dominant modes in the proposed structure. The proposed sensors have the potential to improve current technology\u2019s ability to detect and quantify pure gases.<\/jats:p>","DOI":"10.3390\/s20102807","type":"journal-article","created":{"date-parts":[[2020,5,15]],"date-time":"2020-05-15T10:53:59Z","timestamp":1589540039000},"page":"2807","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":30,"title":["Hollow-Core Photonic Crystal Fiber Mach\u2013Zehnder Interferometer for Gas Sensing"],"prefix":"10.3390","volume":"20","author":[{"given":"Kaveh","family":"Nazeri","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, University of Victoria, Victoria, BC V8W 2Y2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5307-6960","authenticated-orcid":false,"given":"Farid","family":"Ahmed","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8115-5877","authenticated-orcid":false,"given":"Vahid","family":"Ahsani","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Victoria, Victoria, BC V8W 2Y2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hang-Eun","family":"Joe","sequence":"additional","affiliation":[{"name":"School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Colin","family":"Bradley","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Victoria, Victoria, BC V8W 2Y2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ehsan","family":"Toyserkani","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0512-7209","authenticated-orcid":false,"given":"Martin","family":"Jun","sequence":"additional","affiliation":[{"name":"School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,5,15]]},"reference":[{"key":"ref_1","first-page":"9919","article-title":"Solid-state gas sensors for high temperature applications a review","volume":"2","author":"Liu","year":"2014","journal-title":"J. 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