Refractive Index Detection With a Laser-Induced Graphene-Coated Tilted Fiber Bragg Grating and Spectral Profile Interrogation

Marzhan Nurlankyzy, Lucas Pereira, Aida Zhakypbekova, Aliya Bekmurzayeva, Zhannat Ashikbayeva, Andreas Ioannou, Kyriacos Kalli, F.M. Costa, Nuno F. Santos, Carlos Marques

1 more author

Daniele Tosi

2025

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DOI 10.1109/lsens.2025.3598079

Data confidence 85 high

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Abstract

In this letter, we report a tilted fiber Bragg grating (TFBG) with a laser-induced graphene coating. The device displays a cladding mode pattern with a bandwidth of 44 nm. Each spectral dip and peak senses the refractive index change, with sensitivities up to 9.62 dB/refractive index units (RIUs) and 4.00 dB/RIU, respectively. The interrogation of the whole spectral feature envelope can be performed either in the wavelength or in the amplitude domain, with sensitivities of 11.21 nm/RIU and 7.15 dB/RIU, respectively. The graphene-coated TFBG provides improved sensitivity over a standard TFBG with a simple fabrication process and does not require additional components (such as polarizers or intensity-modulating devices) or fiber manipulations (such as etching, tapering, or capillaries). The achieved precision of up to 4.17 × 10-4RIU is compatible with refractometry and biosensing applications.