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Open AccessArticle

A Refractive Index Sensor Based on a Fabry–Perot Interferometer Manufactured by NIR Laser Microdrilling and Electric Arc Fusion

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Laboratório de Óptica, Lasers e Sistemas, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
2
Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
*
Author to whom correspondence should be addressed.
This paper is an extended version of our paper: Nespereira, M.; Coelho, J.M.P.; Rebordão, J. In line Fabry-Perot cavities manufactured by electric arc fusion of NIR-laser microdrilled optical fiber flat tips. 4th International Conference on Applications of Optics and Photonics, Costa MF, Coelho JMP, Cabral A. (Eds); SPOF, 2019, 99.
Photonics 2019, 6(4), 109; https://doi.org/10.3390/photonics6040109
Received: 23 September 2019 / Revised: 18 October 2019 / Accepted: 21 October 2019 / Published: 24 October 2019
In-line Fabry–Perot 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−1/RIU and about 8 nm−1/RIU using the latter method and between about 34 dB/RIU and 54 dB/RIU when analyzing the fringe visibility. View Full-Text
Keywords: Fabry–Perot interferometer; fiber sensors; microdrilling; Nd:YAG laser manufacturing; glass ablation Fabry–Perot interferometer; fiber sensors; microdrilling; Nd:YAG laser manufacturing; glass ablation
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Nespereira, M.; Coelho, J.M.P.; Rebordão, J.M. A Refractive Index Sensor Based on a Fabry–Perot Interferometer Manufactured by NIR Laser Microdrilling and Electric Arc Fusion. Photonics 2019, 6, 109.

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