Femtosecond Laser-written Long Period Fibre Gratings coated with Titanium Dioxide for improved sensitivity

• Type: Article in International Conference Proceedings Book
• Date: 2020

Authors

Viveiros, D (Author) FCUP; de Almeida, JMMM (Author) FCUP; Coelho, L (Author) FCUP; Vasconcelos, H (Author) Other; Amorim, VA (Author) Other; Maia, JM (Author) Other; Jorge, PAS (Author) FCUP; Marques, PVS (Author) FCUP

Conference proceedings International

Title: OPTICAL SENSING AND DETECTION VI

Conference on Optical Sensing and Detection VI

ELECTR NETWORK, APR 06-10, 2020

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Authenticus ID: P-00R-Y3Y

DOI: 10.1117/12.2555686

Abstract (EN): Long Period Fibre Gratings (LPFGs) were fabricated by femtosecond (fs) laser direct writing in a standard single-mode fibre (SMF-28e) to measure variations in the surrounding refractive index (SRI). The sensing sensitivity of these structures was optimized with the deposition of homogeneous thin layers of titanium dioxide (TiO2) by physical vapour deposition (PVD) process. A set of LPFGs were coated with different thickness layers of TiO2, and the spectral features were monitored for different SRI solutions. The wavelength shift and the optical power variation of the LPFG minimum attenuation band were measured achieving sensitivities of similar to 570 nm/RIU at using SRI near to 1.3600 in the case of the LPFG coated with 60 nm of TiO2, a 10-fold increase over the corresponding for a bare LPFG. For SRI values higher than the cladding refractive index, a sensitivity over similar to 3000 nm/RIU was determined for 30 nm of TiO2 thick film, a region where the bare LPFGs are useless. For 30 nm of TiO2, the optical power variation follows a quasi-linear function of the SRI, with a range of similar to 10 dB. Moreover, values as high as 50 and 120 dB/RIU at 1.3200 and 1.4200, respectively, can be obtained by choosing the proper film thickness. Preliminary studies revealed that coating fs-laser direct writing LPFGs with titanium dioxide improves their performance.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7