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Detalhes

Detalhes

011
Publicações

2020

Preface

Autores
Frazão, O; del Villar, I; Fabris, J; Gong, Y;

Publicação
Optics & Laser Technology

Abstract

2020

Preface

Autores
Frazao, O; del Villar, I; Fabris, J; Gong, Y;

Publicação
OPTICS AND LASER TECHNOLOGY

Abstract

2020

Tuning of Fiber Optic Surface Reflectivity through Graphene Oxide-Based Layer-by-Layer Film Coatings

Autores
Monteiro, CS; Raposo, M; Ribeiro, PA; Silva, SO; Frazao, O;

Publicação
Photonics

Abstract
The use of graphene oxide-based coatings on optical fibers are investigated, aiming to tune the reflectivity of optical fiber surfaces for use in precision sensing devices. Graphene oxide (GO) layers are successfully deposited onto optical fiber ends, either in cleaved or hollow microspheres, by mounting combined bilayers of polyethylenimine (PEI) and GO layers using the Layer-by-Layer (LbL) technique. The reflectivity of optical fibers coated with graphene oxide layers is investigated for the telecom region allowing to both monitor layer growth kinetics and cavity characterization. Tunable reflective surfaces are successfully attained in both cleaved optical fibers and hollow microsphere fiber-based sensors by simply coating them with PEI/GO layers through the LbL film technique.

2020

Curvature detection in a medical needle using a Fabry-Perot cavity as an intensity sensor

Autores
Novais, S; Silva, SO; Frazao, O;

Publicação
Measurement: Journal of the International Measurement Confederation

Abstract
The use of optical sensors inside the needle can improve targeting precision and can bring real-time information about the location of the needle tip if necessary, since a needle bends through insertion into the tissue. Therefore, the precise location of the needle tip is so important in percutaneous treatments. In the current experiment, a fiber sensor based on a Fabry-Perot (FP) cavity is described to measure the needle curvature. The sensor is fabricated by producing an air bubble between two sections of multimode fiber. The needle with the sensor therein was attached at one end and deformed by the application of movements. The sensor presents a sensitivity of -0.152 dB/m-1 to the curvature measurements, with a resolution of 0.089 m-1. The sensory structure revealed to be stable, obtaining a cross-sensitivity to be 0.03 m-1/°C. © 2019 Elsevier Ltd

2020

Curvature Sensor Based on a Long-Period Grating in a Fiber Ring Resonator Interrogated by an OTDR

Autores
Magalhaes, R; Silva, S; Frazao, O;

Publicação
Photonic Sensors

Abstract
The proposed technique demonstrates a fiber ring resonator interrogated by an optical time domain reflectometer (OTDR), for intensity sensing. By using this methodology, a cavity round trip time of 2.85 µs was obtained. For a proof of concept, a long-period grating was inserted in the resonant cavity operating as a curvature sensing device. A novel signal processing approach was outlined, regarding to the logarithmic behavior of the OTDR. Through analyzing the experimental results, an increase in the measured sensitivities was obtained by increasing applied bending. With curvatures performed from 1.8 m-1 to 4.5 m-1, the sensitivity values ranged from 2.94 dB·km-1 to 5.15 dB·km-1. In its turn, the sensitivities obtained presented a linear behavior when studied as a function of the applied curvature, following a slope of 0.86×10-3 dB. The advantages of applying this technique were also discussed, demonstrating two similar fiber rings multiplexed in a series of configurations. © 2019, The Author(s).

Teses
supervisionadas

2019

Surface plasmon resonance excitations and nonlinear phenomena in light-guiding structures based on tapered optical fibers

Autor
Tiago Jorge Mendes Martins

Instituição
UP-FCUP

2019

Raman Spectroscopy in tumoral tissues

Autor
João Manuel Ribeiro Jordão

Instituição
UP-FCUP

2018

Metamatrials on fibre optics platforms

Autor
Tiago Jorge Mendes Martins

Instituição
UP-FCUP

2018

Fabricação de microesferas com aplicação em sistemas caóticos

Autor
Paulo Manuel Ribeiro Robalinho

Instituição
UP-FCUP

2018

endoscopia de raman em fibra ótica

Autor
João Manuel Ribeiro Jordão

Instituição
UP-FCUP