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Publicações

2020

Magnetic field sensors in fused silica fabricated by femtosecond laser micromachining

Autores
Maia, JM; Amorim, VA; Viveiros, D; Marques, PVS;

Publicação
Journal of Physics: Photonics

Abstract

2020

Femtosecond laser direct written off-axis fiber Bragg gratings for sensing applications

Autores
Viveiros, D; Amorim, VA; Maia, JM; Silva, S; Frazao, O; Jorge, PAS; Fernandes, LA; Marques, PVS;

Publicação
Optics and Laser Technology

Abstract
First order off-axis fiber Bragg gratings (FBGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond laser direct writing. A minimum offset distance between the grating and core center of 2.5 µm was found to create a multimode section, which supports two separate fiber modes (LP0,1 and LP1,1), each split into two degenerate polarization modes. The resulting structure breaks the cylindrical symmetry of the fiber, introducing birefringence (˜10-4) resulting in a polarization dependent Bragg wavelength for each mode. Based on the modal and birefringence behavior, three off-axis FBGs were fabricated with 3.0, 4.5 and 6.0 µm offsets from the core center, and then characterized in strain, temperature, and curvature. The tested off-axis FBGs exhibited a similar strain sensitivity of ~1.14 pm/µ? and a temperature sensitivity of ~12 pm/C. The curvature and orientation angle were simultaneously monitored by analyzing the intensity fluctuation and the wavelength shift of the LP1,1 Bragg resonance. A maximum curvature sensitivity of 0.53 dB/m-1 was obtained for the off-axis FBG with a 3.0 µm offset. © 2020 Elsevier Ltd

2020

Femtosecond laser micromachining of Fabry-Perot interferometers in SMF-28 fiber for pressure sensing (Conference Presentation)

Autores
Viveiros, D; Almeida, JMd; Coelho, L; Maia, JM; Amorim, VA; Vasconcelos, H; Jorge, PAS; Marques, PVS;

Publicação
Optical Sensing and Detection VI

Abstract

2020

Femtosecond laser-written long period fibre gratings coated with titanium dioxide for improved sensitivity

Autores
Viveiros, D; De Almeida, JMMM; Coelho, L; Vasconcelos, H; Amorim, VA; Maia, JM; Jorge, PAS; Marques, PVS;

Publicação
Optical Sensing and Detection VI

Abstract

2020

Temperature Stability and Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Direct Writing

Autores
Viveiros, D; de Almeida, JMMM; Coelho, L; Vasconcelos, H; Maia, JM; Amorim, VA; Jorge, PAS; Marques, PVS;

Publicação
Sensors

Abstract
Long period fiber gratings (LPFGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond (fs) laser direct writing. LPFGs with longer and shorter periods were fabricated, which allows coupling from the fundamental core mode to lower and higher order asymmetric cladding modes (LP1,6 and LP1,12, respectively). For the grating periods of 182.7 and 192.5 µm, it was verified that the LP1,12 mode exhibits a TAP at approximately 1380 and 1448 nm in air and water, respectively. Characterization of the LPFGs subjected to high-temperature thermal treatment was accomplished. Fine-tuning of the resonance band’s position and thermal stability up to 600 °C was shown. The temperature sensitivity was characterized for the gratings with different periods and for different temperature ranges. A maximum sensitivity of -180.73, and 179.29 pm/°C was obtained for the two resonances of the 182.7 µm TAP LPFG, in the range between 250 and 600 °C.