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Sobre

Sobre

João M. Maia terminou o Mestrado Integrado em Engenharia Fí­sica na Universidade do Porto, Portugal em 2016. É atualmente estudante do programa doutoral de Física da mesma instituição.

Desde 2015, pertence ao centro de investigação INESC TEC, onde trabalha em micromaquinação com laser femtossegundo e optofluídica.

Tópicos
de interesse
Detalhes

Detalhes

001
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-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.

2020

Inscription of surface waveguides in glass by femtosecond laser writing for enhanced evanescent wave overlap

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

Publicação
JOURNAL OF OPTICS

Abstract
Near-surface optical waveguides were fabricated in alkaline earth boro-aluminosilicate glass (Eagle2000), by femtosecond laser direct writing, using two distinct approaches. First, the capability of directly inscribing optical waveguides close to the surface was tested, and then, compared to the adoption of post writing wet etching to bring to the surface waveguides inscribed at greater depths. Laser ablation was found to limit the minimum surface to core center distance to 6.5 mu m in the first method, with anisotropic wet etching limiting the latter to 3 mu m without any surface deformation; smaller separations can be achieved at the cost of the planar surface topography. Furthermore, the waveguide's cross-section was seen to vary for laser inscription nearing the surface, observations that were also corroborated by its distinct guiding characteristics when compared to the adoption of post writing wet etching. The spectral analysis (in the 500-1700 nm range) also evidenced an increase in insertion loss for longer wavelengths and smaller surface to core center separations, caused, most likely, by coupling loss due to the interaction between the propagating mode and the surface. Different lengths of waveguide exposed to the surface were also tested, revealing that scattering loss due to surface roughness is not an issue at the centimeter scale.