{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:49:12Z","timestamp":1760240952968,"version":"build-2065373602"},"reference-count":19,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2019,10,24]],"date-time":"2019-10-24T00:00:00Z","timestamp":1571875200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UID\/BIO\/00645\/2019"],"award-info":[{"award-number":["UID\/BIO\/00645\/2019"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Photonics"],"abstract":"<jats:p>In-line Fabry\u2013Perot cavities manufactured by a new technique using electric arc fusion of NIR laser microdrilled optical fiber flat tips were studied herein for refractive index sensing. Sensors were produced by creating an initial hole on the tip of a standard single-mode telecommunication optical fiber using a Q-switched Nd:YAG laser. Laser ablation and plasma formation processes created 5 to 10 micron cavities. Then, a standard splicing machine was used to fuse the microdrilled fiber with another one, thus creating cavities with lengths around 100 micrometers. This length has been proven to be necessary to obtain an interferometric signal with good fringe visibility when illuminating it in the C-band. Then, the sensing tip of the fiber, with the resulting air cavity, was submitted to several cleaves to enhance the signal and, therefore, its response as a sensor, with final lengths between tens of centimeters for the longest and hundreds of microns for the shortest. The experimental results were analyzed via two signal analysis techniques, fringe visibility and fast Fourier transform, for comparison purposes. In absolute values, the obtained sensitivities varied between 0.31 nm\u22121\/RIU and about 8 nm\u22121\/RIU using the latter method and between about 34 dB\/RIU and 54 dB\/RIU when analyzing the fringe visibility.<\/jats:p>","DOI":"10.3390\/photonics6040109","type":"journal-article","created":{"date-parts":[[2019,10,25]],"date-time":"2019-10-25T04:41:27Z","timestamp":1571978487000},"page":"109","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A Refractive Index Sensor Based on a Fabry\u2013Perot Interferometer Manufactured by NIR Laser Microdrilling and Electric Arc Fusion"],"prefix":"10.3390","volume":"6","author":[{"given":"Marta","family":"Nespereira","sequence":"first","affiliation":[{"name":"Laborat\u00f3rio de \u00d3ptica, Lasers e Sistemas, Faculdade de Ci\u00eancias, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4339-0550","authenticated-orcid":false,"given":"Jo\u00e3o M. P.","family":"Coelho","sequence":"additional","affiliation":[{"name":"Laborat\u00f3rio de \u00d3ptica, Lasers e Sistemas, Faculdade de Ci\u00eancias, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal"},{"name":"Instituto de Biof\u00edsica e Engenharia Biom\u00e9dica, Faculdade de Ci\u00eancias, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal"}]},{"given":"Jos\u00e9 M.","family":"Rebord\u00e3o","sequence":"additional","affiliation":[{"name":"Laborat\u00f3rio de \u00d3ptica, Lasers e Sistemas, Faculdade de Ci\u00eancias, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2019,10,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"7451","DOI":"10.3390\/s140407451","article-title":"Chronology of Fabry-Perot interferometer fiber-optic sensors and their applications: A review","volume":"14","author":"Islam","year":"2014","journal-title":"Sensors"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"13280","DOI":"10.1364\/OE.27.013280","article-title":"Miniature, micro-machined, fiber-optic Fabry-Perot voltage sensor","volume":"27","author":"Javernik","year":"2019","journal-title":"Opt. Express"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Liang, H., Jia, P., Liu, J., Fang, G., Li, Z., Hong, Y., Liang, T., and Xiong, J. (2018). Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application. Sensors, 18.","DOI":"10.3390\/s18041011"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Cheng, J., Zhou, Y., and Zou, X. (2018). Fabry-Perot Cavity Sensing Probe with High Thermal Stability for an Acoustic Sensor by Structure Compensation. Sensors, 18.","DOI":"10.3390\/s18103393"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"9556","DOI":"10.1038\/s41598-019-45909-2","article-title":"Optical fibre Fabry-P\u00e9rot interferometer based on inline microcavities for salinity and temperature sensing","volume":"9","author":"Flores","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Budinski, V., and Donlagic, D.A. (2019). Miniature Fabry Perot Sensor for Twist\/Rotation, Strain and Temperature Measurements Based on a Four-Core Fiber. Sensors, 19.","DOI":"10.3390\/s19071574"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"22813","DOI":"10.1364\/OE.20.022813","article-title":"Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing","volume":"20","author":"Liao","year":"2012","journal-title":"Opt. Express"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1033","DOI":"10.1364\/AO.51.001033","article-title":"Microbubble based fiber-optic Fabry\u2013Perot interferometer formed by fusion splicing single-mode fibers for strain measurement","volume":"51","author":"Duan","year":"2012","journal-title":"Appl. Opt."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Yan, L., Gui, Z., Wang, G., An, Y., Gu, J., Zhang, M., Liu, X., Wang, Z., Wang, G., and Jia, P. (2017). A micro bubble structure based Fabry\u2013Perot optical fiber strain sensor with high sensitivity and low-cost characteristics. Sensors, 17.","DOI":"10.3390\/s17030555"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"339","DOI":"10.1007\/s13320-016-0333-9","article-title":"Fiber Fabry-Perot interferometer for curvature sensing","volume":"6","author":"Monteiro","year":"2016","journal-title":"Photonic Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2035","DOI":"10.1109\/LPT.2015.2449654","article-title":"Polymer microbubble-based Fabry\u2013Perot fiber interferometer and sensing applications","volume":"27","author":"Tan","year":"2015","journal-title":"IEEE Photonic Technol. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"60","DOI":"10.1016\/j.sna.2018.03.044","article-title":"High sensitivity temperature sensor based on fiber air-microbubble Fabry-Perot interferometer with PDMS-filled hollow-core fiber","volume":"275","author":"Chen","year":"2018","journal-title":"Sens. Actuator A Phys."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1109\/JSTQE.2015.2497438","article-title":"Miniature pH optical fiber sensor based on Fabry\u2013Perot interferometer","volume":"22","author":"Zheng","year":"2015","journal-title":"IEEE J. Sel. Top. Quantum Electron."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1016\/j.optcom.2013.11.028","article-title":"Femtosecond laser fabricated in-line micro multicavity fiber FP interferometers sensor","volume":"316","author":"Tian","year":"2014","journal-title":"Opt. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1016","DOI":"10.1016\/j.snb.2017.01.081","article-title":"Sensing with ultra-short Fabry-Perot cavities written into optical micro-fibers","volume":"244","author":"Dellith","year":"2017","journal-title":"Sens. Actuator B Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1813","DOI":"10.1109\/LPT.2015.2443375","article-title":"Open-cavity fabry-perot interferometer based on etched side-hole fiber for microfluidic sensing","volume":"27","author":"Wu","year":"2015","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2252","DOI":"10.1364\/OE.16.002252","article-title":"Laser-micromachined Fabry-Perot optical fiber tip sensor for high-resolution temperature-independent measurement of refractive index","volume":"16","author":"Ran","year":"2018","journal-title":"Opt. Express"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Nespereira, M., Silva, C., Coelho, J., and Rebord\u00e3o, J. (2011, January 3\u20137). Nanosecond laser micropatterning of optical fibers. Proceedings of the International Conference on Applications of Optics and Photonics, Braga, Portugal.","DOI":"10.1117\/12.892087"},{"key":"ref_19","unstructured":"Nespereira, M., Coelho, J., and Rebord\u00e3o, J. (June, January 31). In line Fabry-Perot cavities manufactured by electric arc fusion of NIR-laser micro-drilled optical fiber flat tips. Proceedings of the Fourth International Conference on Applications of Optics and Photonics, Lisbon, Portugal."}],"container-title":["Photonics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2304-6732\/6\/4\/109\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:29:05Z","timestamp":1760189345000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2304-6732\/6\/4\/109"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,10,24]]},"references-count":19,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2019,12]]}},"alternative-id":["photonics6040109"],"URL":"https:\/\/doi.org\/10.3390\/photonics6040109","relation":{},"ISSN":["2304-6732"],"issn-type":[{"type":"electronic","value":"2304-6732"}],"subject":[],"published":{"date-parts":[[2019,10,24]]}}}