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Publications

Publications by Paulo Vicente Marques

2022

Femtosecond laser micromachining of suspended silica-core liquid-cladding waveguides inside a microfluidic channel

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

Publication
OPTICS AND LASERS IN ENGINEERING

Abstract
This work addresses the fabrication of straight silica-core liquid-cladding suspended waveguides inside a microfluidic channel through fs-laser micromachining. These structures enable the reconfiguration of the waveguide's mode profile and enhance the evanescent interaction between light and analyte. Further, their geometry resembles a tapered optical fiber with the added advantage of being monolithically integrated within a microfluidic platform. The fabrication process includes an additional post-processing thermal treatment responsible for smoothening the waveguide surface and reshaping it into a circular cross-section. Suspended waveguides with a minimum core diameter of 3.8 mu m were fabricated. Their insertion losses can be tuned and are mainly affected by mode mismatch between the coupling and suspended waveguides. The transmission spectrum was studied and it was numerically confirmed that it consists of interference between the guided LP01 mode and uncoupled light and of modal interference between the LP01 and LP02 modes.

2020

Femtosecond Laser Direct Writing of Turn Around Point Long Period Fiber Gratings Coated with Titanium Dioxide for Improved Sensitivity

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

Publication
Optics InfoBase Conference Papers

Abstract
The fabrication of Turn Around Point Long Period Fiber Grating in standard SMF-28e fibers through femtosecond laser direct writing is demonstrated and its sensing sensitivity is improved by coating the fiber with titanium dioxide through physical vapor deposition. © 2021 The Author(s).

2020

Off-axis Fiber Bragg Grating Fabricated by Femtosecond Laser Direct Writing for Torsion Sensing

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

Publication
Optics InfoBase Conference Papers

Abstract
The precise production of 4.5 µm off-axis first order FBG in an SMF-28e fiber through femtosecond laser direct writing is demonstrated. The off-axis FBG potential as sensing head for torsion sensing was successfully explored. © 2021 The Author(s).

2020

Characterization of Femtosecond Laser Direct Written Mach-Zehnder Interferometers Based on Titanium Dioxide Coated Long Period Fiber Gratings

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

Publication
Optics InfoBase Conference Papers

Abstract
Optical fiber Mach-Zehnder interferometers were fabricated by combining two TiO2 coated LPFGs fabricated through femtosecond laser direct writing. Results of its refractometric characterization are presented and compared with the single LPFGs sensors. Wavelength sensitivity of 1175 nm/RIU at 1.38 and spectral resolution of 2.2×10-5 were achieved. © 2021 The Author(s).

2022

The effect of frequency modulation on the FSR of a Fabry-Perot cavity using an Optical Spectrum Analyser

Authors
Reis, J; V.Rodrigues, A; Robalinho, P; Novais, S; Maia, J; Marques, P; Roma, D; Salvans, J; Canal, M; Ramos, J; Gualani, V; Sisteré, S; Martín, V; Nofrarias, M; Silva, S; Frazão, O;

Publication
EPJ Web of Conferences

Abstract
It is presented a study of the dependence between the free spectral range (FSR) and the cavity length in Fabry-Perot interferometers. Furthermore, the effect of frequency modulation on the FSR is studied when an optical spectrum analyser (OSA) is used as an interrogator. For low frequency range it is possible to observe this behaviour in the OSA and using an appropriate processing signal it is possible to use the white light interferometry technique.

2006

Investigation of formation mechanisms of arc-induced long-period fiber gratings

Authors
Rego, G; Ivanov, OV; Marques, PVS; Santos, JL;

Publication
Optics InfoBase Conference Papers

Abstract
By measuring intensity distributions of cladding modes and using an optimization technique we show that the perturbation which forms arc-induced gratings in standard fibers is antisymmetric, while the perturbation in boron-germanium codoped fibers is symmetric. © 2006 Optical Society of America.

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