Turn Around Point Long Period Fiber Gratings With Coupling to Asymmetric Cladding Modes Fabricated by a Femtosecond Laser and Coated With Titanium Dioxide

• Type: Article in International Scientific Journal
• Date: 2021

Authors

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

Journal

The Journal is awaiting validation by the Administrative Services.

Title: JOURNAL OF LIGHTWAVE TECHNOLOGY

Vol. 39

Pages: 4784-4793

ISSN: 0733-8724

Indexing

ISI Web of Knowledge - 10 Citations

Scopus - 10 Citations

Other information

Authenticus ID: P-00V-7AW

DOI: 10.1109/jlt.2021.3078257

Abstract (EN): A detailed study of turn around point (TAP) long period fiber gratings (LPFGs) with coupling to the asymmetric cladding modes of a standard single-mode fiber (SMF-28e), fabricated by femtosecond (fs) laser direct writing was realized. The entire fabrication process, including the coating with different titanium dioxide (TiO2) film thicknesses of LPFGs and the corrections needed to achieve coated devices operating precisely in the TAP condition with coupling to the asymmetric cladding modes, was addressed. The significant fabrication details are also given, such as inscription periods, shape and localization of the refractive index modifications across the core. The fabrication process described allows the optimization of the LPFGs sensitivity in regards to the surrounding refractive index (SRI). Optimization of the writing parameters to obtain gratings working at the TAP for two different media surrounding the fiber (water and air) was achieved. It was demonstrated that for a grating period of 191.8 mu m, the LP1,12 mode exhibits a TAP at 1442.7 nm in air, and for a period of 192.5 mu m, the same mode exhibits a TAP at 1448.6 nm in water. The LPFGs operating at the TAP in air and water were coated with 10, 20, and 30 nm thin TiO2 film thicknesses and the spectral behavior characterized. The wavelength sensitivity to the surrounding refractive index (SRI) was assessed in the range between 1.3700 to 1.4120, and a maximum sensitivity of similar to 8051.4 nm/RIU was measured for the 192.5 mu m LPFG coated with a 30 nm thick TiO2 film.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10