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André Gomes completou o seu mestrado integrado em Engenharia Física na Faculdade de Ciências da Universidade do Porto, Porto, Portugal. É atualmente estudante de doutoramento, também na Universidade do Porto. De Março a Julho de 2016, ele esteve no Leibniz Institute of Photonic Technology, em Jena, na Alemanha, com uma bolsa de estudo da DAAD. Atualmente está no Centro de Photonica Aplicada do INESC TEC. Os seus interesses incluem sensores em fibra óptica, micro e nanofibras, tecnologia de feixe de iões focados (Focused Ion Beam) e nós resoadores em microfibra (microfiber knot resonators).

Tópicos
de interesse
Detalhes

Detalhes

Publicações

2020

Hollow microsphere combined with optical harmonic Vernier effect for strain and temperature discrimination

Autores
Gomes, AD; Ferreira, MS; Bierlich, J; Kobelke, J; Rothhardt, M; Bartelt, H; Frazao, O;

Publicação
OPTICS AND LASER TECHNOLOGY

Abstract
Achieving a new generation of enhanced sensors requires the development of structures that result from the fusion of different concepts and effects. In this paper, we combine a special strain sensing structure with an optical sensitivity magnification, through harmonics of the Vernier effect. The recently demonstrated harmonics of the Vernier effect result from increasing the optical path length (OPL) of one of two interferometers by multiple times the OPL of the other interferometer. The effect generates higher magnification factors, proportional to the order of the harmonics. The sensing structure is demonstrated for strain and temperature discrimination, allowing compensation for temperature fluctuations. We explore the complex case of the optical Vernier effect in series, where both interferometers are used as sensing interferometers (no reference interferometer is used). Our results also suggest that the magnification enhancement provided by harmonics of the Vernier effect for a configuration in series is the same as for a configuration in parallel: the magnification factor increases proportionally to the order of the harmonics.

2020

High Enhancement Strain Sensor based on Vernier Effect using 2-Fiber Loop Mirrors

Autores
Robalinho, P; Gomes, AD; Frazao, O;

Publicação
IEEE Photonics Technology Letters

Abstract

2019

Multimode Fabry?Perot Interferometer Probe Based on Vernier Effect for Enhanced Temperature Sensing

Autores
Gomes, AD; Becker, M; Dellith, J; Zibaii, MI; Latifi, H; Rothhardt, M; Bartelt, H; Frazao, O;

Publicação
Sensors (Basel, Switzerland)

Abstract
New miniaturized sensors for biological and medical applications must be adapted to the measuring environments and they should provide a high measurement resolution to sense small changes. The Vernier effect is an effective way of magnifying the sensitivity of a device, allowing for higher resolution sensing. We applied this concept to the development of a small-size optical fiber Fabry?Perot interferometer probe that presents more than 60-fold higher sensitivity to temperature than the normal Fabry?Perot interferometer without the Vernier effect. This enables the sensor to reach higher temperature resolutions. The silica Fabry?Perot interferometer is created by focused ion beam milling of the end of a tapered multimode fiber. Multiple Fabry?Perot interferometers with shifted frequencies are generated in the cavity due to the presence of multiple modes. The reflection spectrum shows two main components in the Fast Fourier transform that give rise to the Vernier effect. The superposition of these components presents an enhancement of sensitivity to temperature. The same effect is also obtained by monitoring the reflection spectrum node without any filtering. A temperature sensitivity of -654 pm/°C was obtained between 30 °C and 120 °C, with an experimental resolution of 0.14 °C. Stability measurements are also reported.

2019

Microfiber Knot Resonators for Sensing Applications

Autores
Gomes, AD; Frazao, O;

Publicação
Springer Series in Optical Sciences

Abstract
Microfiber knot resonators are widely applied in many different fields of action, of which an important one is the optical sensing. Microfiber knot resonators can easily be used to sense the external medium. The large evanescent field of light increase the interaction of light with the surrounding medium, tuning the resonance conditions of the structure. In some cases, the ability of light to give several turns in the microfiber knot resonator allows for greater interaction with deposited materials, providing an enhancement in the detection capability. So far a wide variety of physical and chemical parameters have been possible to measure using microfiber knot resonators. However, new developments and improvements are still being done in this field. In this chapter, a review on sensing with microfiber knot resonators is presented, with particular emphasis on the application of these structures as temperature and refractive index sensors. A detailed analysis on the properties of these structures and different assembling configurations is presented. An important discussion regarding the sensor stability is presented, as well as alternatives to increase the device robustness. An overview on the recent developments in coated microfiber knot resonators is also addressed. In the end, other microfiber knot configurations are explored and discussed. © 2019, Springer Nature Switzerland AG.

2019

Optical Fiber Probe Viscometer Based on Hollow Capillary Tube

Autores
Gomes, AD; Kobelke, J; Bierlich, J; Schuster, K; Bartelt, H; Frazao, O;

Publicação
JOURNAL OF LIGHTWAVE TECHNOLOGY

Abstract
Viscosity measurements of a solution are crucial for many processes involving fluid flows. The current optical fiber viscometers are complex and, in some cases, provide indirect measurements of viscosity through other non-optical effects. We developed a miniaturized optical fiber probe capable of providing an optical interferometric measurement of the viscosity of small volumes of a liquid viscous medium (less than 50 pL). The probe consists of an air cavity with a small access hole for fluids, which resulted from a simple post-processing of a hollow capillary tube. The structure behaves as a two-wave interferometer, where the intensity of the signal is sensible to the position of the air-fluid interface inside the cavity. The fluid displacement over time is obtained by monitoring the signal intensity variations, at 1550 nm, during the process of removing the sensing head from a fluid solution. Multiple sucrose solutions with viscosities ranging from 2.01 to 16.1 mPa.s were used for calibration. The viscosity of the solution is measured through the fluid evacuation velocity in the first 300 ms of resolved oscillations during the evacuation process. Reproducibility measurements, the influence of temperature, and the access hole dimensions are also addressed. The application to biological fluids is important to be considered in future studies.