{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T02:13:51Z","timestamp":1776132831486,"version":"3.50.1"},"reference-count":32,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2019,6,29]],"date-time":"2019-06-29T00:00:00Z","timestamp":1561766400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Government of Spain","award":["TEC2017-86271-R"],"award-info":[{"award-number":["TEC2017-86271-R"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A sensitive optical microphone for photoacoustic spectroscopy based on the common path topology of a fibre laser Doppler vibrometer (FLDV) using phase-generated carrier demodulation and a slim diaphragm as an acoustic wave transducer was demonstrated. A resonant gas cell was adapted to enhance gas-detection performance and simultaneously provide efficient cancellation of the window background acoustic signal. Ammonia (NH3) was selected as the target gas. The absorption line was experimentally identified using a distributed feedback laser diode emitting at 1530 nm. The linearity and sensitivity of the gas sensor were measured using wavelength modulation spectroscopy with second harmonic detection. A Teflon diaphragm was used to implement the optical microphone, along with the FLDV, showing a minimum detectable pressure of 79.5 \u03bcPa\/Hz1\/2. The noise-equivalent absorption sensitivity for NH3 detection at the absorption line at 1531.7 nm was 1.85 \u00d7 10\u22128 W cm\u22121 Hz\u22121\/2, and the limit of detection was 785 ppbv.<\/jats:p>","DOI":"10.3390\/s19132890","type":"journal-article","created":{"date-parts":[[2019,7,1]],"date-time":"2019-07-01T03:23:59Z","timestamp":1561951439000},"page":"2890","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":28,"title":["Sub-ppm-Level Ammonia Detection Using Photoacoustic Spectroscopy with an Optical Microphone Based on a Phase Interferometer"],"prefix":"10.3390","volume":"19","author":[{"given":"Oscar E.","family":"Bonilla-Manrique","sequence":"first","affiliation":[{"name":"Electronics Technology Department, Carlos III University of Madrid, 28911 Legan\u00e9s, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0587-7907","authenticated-orcid":false,"given":"Julio E.","family":"Posada-Roman","sequence":"additional","affiliation":[{"name":"Electronics Technology Department, Carlos III University of Madrid, 28911 Legan\u00e9s, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9839-2898","authenticated-orcid":false,"given":"Jose A.","family":"Garcia-Souto","sequence":"additional","affiliation":[{"name":"Electronics Technology Department, Carlos III University of Madrid, 28911 Legan\u00e9s, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6361-4681","authenticated-orcid":false,"given":"Marta","family":"Ruiz-Llata","sequence":"additional","affiliation":[{"name":"Electronics Technology Department, Carlos III University of Madrid, 28911 Legan\u00e9s, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,6,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Harren, F.J.M., Mandon, J., and Cristescu, S.M. 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