Cookies Policy
We use cookies to improve our site and your experience. By continuing to browse our site you accept our cookie policy. Find out More
Close
  • Menu
About

About

André Gomes completed his master degree in Engineering Physics at the Faculty of Sciences of the University of Porto, Porto, Portugal. He is currently a PhD student in physics, also at the University of Porto. From March to July 2016, he was with the Leibniz Institute of Photonic Technology, in Jena, Germany, with a DAAD scholarship. At the moment, he is with the Center of Applied Photonics at INESC TEC. His research interests include optical fiber sensing, micro and nanofibers, Focused Ion Beam technology and microfiber knot resonators.


Interest
Topics
Details

Details

Publications

2019

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

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

Publication
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

Optical Fiber Probe Viscometer Based on Hollow Capillary Tube

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

Publication
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.

2019

Enhanced temperature sensing with Vernier effect on fiber probe based on multimode Fabry-Perot interferometer

Authors
Gomes, AD; Becker, M; Dellith, J; Zibaii, MI; Latifi, H; Rothhardt, M; Bartelt, H; Frazaõ, O;

Publication
Proceedings of SPIE - The International Society for Optical Engineering

Abstract
Sensing at small dimensions in biological and medical environments requires miniaturized sensors with high sensitivity and measurement resolution. In this work a small optical fiber probe was developed to apply the Vernier effect, allowing for enhanced temperature sensing. Such effect is an effective way of magnifying the sensitivity of a sensor or measurement system in order to reach higher resolutions. The device is a multimode silica Fabry-Perot interferometer structured at the edge of a tapered multimode fiber by focused ion beam milling. The Vernier effect is generated from the interference between different modes in the Fabry-Perot interferometer. The sensor was characterized in temperature, achieving a sensitivity of-654 pm/°C in a temperature range from 30°C to 120°C. The Vernier effect provided a temperature sensitivity over 60-fold higher than the sensitivity of a normal silica Fabry-Perot interferometer without the effect. The temperature resolution obtained was 0.14°C, however this value was limited by the resolution of the OSA and can be improved further to less than 0.015°C. © 2019 SPIE.

2018

Temperature independent refractive index measurement using a fiber Bragg grating on abrupt tapered tip

Authors
Gomes, AD; Silveira, B; Warren Smith, SC; Becker, M; Rothhardt, M; Frazao, O;

Publication
Optics and Laser Technology

Abstract
A fiber Bragg grating was inscribed in an abrupt fiber taper using a femtosecond laser and phase-mask interferometer. The abrupt taper transition allows to excite a broad range of guided modes with different effective refractive indices that are reflected at different wavelengths according to Bragg's law. The multimode-Bragg reflection expands over 30 nm in the telecom-C-band. This corresponds to a mode-field overlap of up to 30% outside of the fiber, making the device suitable for evanescent field sensing. Refractive index and temperature measurements are performed for different reflection peaks. Temperature independent refractive index measurements are achieved by considering the difference between the wavelength shifts of two measured reflection peaks. A minimum refractive index sensitivity of 16 ± 1 nm/RIU was obtained in a low refractive index regime (1.3475–1.3720) with low influence of temperature (-0.32 ± 0.06 pm/°C). The cross sensitivity for this structure is 2.0 × 10-5 RIU/°C. The potential for simultaneous measurement of refractive index and temperature is also studied. © 2017 Elsevier Ltd

2018

Cleaved Silica Microsphere for Temperature Measurement

Authors
Gomes, AD; Silveira, B; Dellith, J; Becker, M; Rothhard, M; Bartelt, H; Frazao, O;

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
A sensing structure based on a cleaved silica microsphere is proposed for temperature sensing. The microsphere was cleaved using focused ion beam milling. The asymmetry in the structure introduced by the cut generates not only new cavities but also random interferometric reflections inside the microsphere. These two spectral components can be separated using low-pass and high-pass filters, respectively. The sensor response to temperature can be extracted from the cavities' component using a correlation method. The device achieved a temperature sensitivity of -10.8 +/- 0.2 pm/degrees C between 30 degrees C and 80 degrees C. The same effect is impossible to be obtained in a normal uncleaved microsphere. The random interferometric component did not provide any information on temperature using the same analysis. However, when changing the temperature, a new and completely distinct reflection spectrum with no apparent correlation with others at different temperatures was achieved.