Refractive index sensor based on the micromachined side-hole optical fibre

An intensity-based refractive index (RI) sensor using a laser micromachined side-hole optical fibre (S-H OF) is presented in this paper. To achieve this, a microcavity was cut into a side surface of the S-H OF, providing access to one of the air holes within its structure. The geometrically modified fibre was then connected at both ends to a single-mode fibre for structure investigation in a system containing a supercontinuum laser and an optical signal analyser. In the next step, an immersion liquid was applied to a microcavity for RI values ranging from 1.30 to 1.57 in increments of 0.02. Power loss measurements were conducted for each RI value. Based on the obtained results, it can be concluded that an RI sensor has been successfully developed, which holds potential applications in biochemistry.

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1. Opracowanie rekordu ze środków MNiSW, umowa nr POPUL/SP/0154/2024/02 w ramach programu "Społeczna odpowiedzialność nauki II" - moduł: Popularyzacja nauki (2025).

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2. This research was financially supported by the Military University of Technology under research project UGB. The S-H OF used in the research was kindly provided by the Laboratory of Optical Fibers Technology at Maria Curie-Skłodowska University in Lublin, Poland.