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About

Recently got a Msc degree in Physics engineering, from Porto University. Currently works at Center of applied photonics at INESCTEC as recearch assistant. Current research lies on advanced Interrogation techniques for optical sensors based on microcavities; Development of low-cost interrogation systems for long-period fiber gratings(LPG) for corrosion sensing in metallic structures. Interrogation techniques using LPG or fiber Bragg gratings (FGB) for health assessment of concrete structures.

Interest
Topics
Details

Details

  • Nationality

    Portugal
  • Centre

    Applied Photonics
  • Contacts

    +351220402301
    paulo.s.santos@inesctec.pt
003
Publications

2022

Study of LSPR Spectral Analysis Techniques on SPR Optical Fiber Sensors

Authors
Dos Santos, PSS; de Almeida, JMMM; Coelho, LCC;

Publication
U.Porto Journal of Engineering

Abstract
Nanoparticles create localized surface plasmonic resonances (LSPR) with lower surrounding refractive index (SRI) sensitivities than their propagating SPR counterpart, originated in thin films. Historically, LSPR SRI sensitivities enhancements were achieved through spectral analysis methods that focus on unique spectral features. Herein, a study using that methodology was applied on SPR devices resulting in an increased sensitivity to SRI. It was found that by applying the inflection point method on optical fiber SPR sensors resulted in both sensitivity and resolution increments up to 44 and 35 %, respectively, in the SRI range from 1.3333 to 1.4150. Thus, successfully improving sensing capabilities of SPR based optical fiber sensors.

2021

Development of a Long Period Fiber Grating Interrogation System Using A Multimode Laser Diode

Authors
Silva, LH; Santos, P; Coelho, LCC; Jorge, P; Baptista, JM;

Publication
SENSORS

Abstract
Optical fiber gratings have long shown their sensing capabilities. One of the main challenges, however, is the interrogation method applied, since typical systems tend to use broadband light sources with optical spectrum analyzers, laser scanning units or CCD (Charged Coupled Device) spectrometers. The following paper presents the development of an interrogation system, which explores the temperature response of a multimode laser diode, in order to interrogate long period fiber gratings. By performing a spectral sweep along one of its rejection bands, a discrete attenuation spectrum is created. Through a curve fitting technique, the original spectrum is restored. The built unit, while presenting a substantially reduced cost compared with typical interrogation systems, is capable of interrogating along a 10 nm window with measurement errors reaching minimum values as low as 0.4 nm, regarding the grating central wavelength, and 0.4 dB for its attenuation. Given its low cost and reduced dimensions, the developed system shows potential for slow-changing field applications.

2021

Advances in plasmonic sensing at the nir—a review

Authors
Dos Santos, PSS; De Almeida, JMMM; Pastoriza Santos, I; Coelho, LCC;

Publication
SENSORS

Abstract
Surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) are among the most common and powerful label-free refractive index-based biosensing techniques available nowadays. Focusing on LSPR sensors, their performance is highly dependent on the size, shape, and nature of the nanomaterial employed. Indeed, the tailoring of those parameters allows the development of LSPR sensors with a tunable wavelength range between the ultra-violet (UV) and near infra-red (NIR). Furthermore, dealing with LSPR along optical fiber technology, with their low attenuation coefficients at NIR, allow for the possibility to create ultra-sensitive and long-range sensing networks to be deployed in a variety of both biological and chemical sensors. This work provides a detailed review of the key science underpinning such systems as well as recent progress in the development of several LSPR-based biosensors in the NIR wavelengths, including an overview of the LSPR phenomena along recent developments in the field of nanomaterials and nanostructure development towards NIR sensing. The review ends with a consideration of key advances in terms of nanostructure characteristics for LSPR sensing and prospects for future research and advances in this field. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

2019

Low-cost interrogation system for long-period fiber gratings applied to remote sensing

Authors
dos Santos, PSS; Jorge, PAS; de Almeida, JMMM; Coelho, L;

Publication
SENSORS

Abstract
We present a portable and low-cost system for interrogation of long-period fiber gratings (LPFGs) costing around a 30th of the price of a typical setup using an optical spectrum analyzer and a broadband light source. The unit is capable of performing real-time monitoring or as a stand-alone data-logger. The proposed technique uses three thermally modulated fiber-coupled laser diodes, sweeping a few nanometers around their central wavelength. The light signal is then modulated by the LPFG and its intensity is acquired by a single photo-detector. Through curve-fitting algorithms the sensor transmission spectrum is reconstructed. Testing and validation were accomplished by inducing variations in the spectral features of an LPFG through changes either in external air temperature from 22 to 425 °C or in refractive index (RI) of the surrounding medium from 1.3000 to 1.4240. A dynamic resolution between 3.5 and 1.9 °C was achieved, in temperatures from 125 to 325 °C. In RI measurements, maximum wavelength and optical power deviations of 2.75 nm and 2.86 dB, respectively, were obtained in the range from 1530 to 1570 nm. The worse RI resolution obtained was 3.47 × 10 -3 . The interrogation platform was then applied in the detection of iron corrosion, expressing wavelength peak values within 1.12 nm from the real value in the region between 1530 and 1570 nm. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

2018

Real-time Early Warning Strategies for Corrosion Mitigation in Harsh Environments

Authors
Costa Coelho, LCC; Soares dos Santos, PSS; da Silva Jorge, PAD; Santos, JL; Marques Martins de Almeida, JMMM;

Publication
JOURNAL OF LIGHTWAVE TECHNOLOGY

Abstract
Long period fiber gratings (LPFGs) were coated with iron (Fe) and exposed to oxidation in air and in water having different concentrations of sodium chloride (NaCl) to detect the formation of iron oxides and hydroxides. The process was monitored in real time by measuring the characteristics of the LPFGs attenuation bands. Thin films of Fe were deposited on top of silica (SiO2) substrates, annealed in air, and exposed to water with NaCl. The composition of the oxide and hydroxide layers were analyzed by SEM/EDS and XRD. It was observed the formation of oxide phases, Fe3O4 (magnetite) and Fe2O3 (hematite) when annealing in air, and Fe2(OH)3Cl (hibbingite) and FeO(OH) (lepidocrocite) when exposed to water with NaCl. Results shows that Fe coated LPFGs can be used as sensors for real time monitoring of corrosion in offshore and in coastal projects where metal structures made of iron alloys are in contact with sea or brackish water. In addition, LPFGs coated with hematite were characterized for sensing, leading to the conclusion that the sensitivity to the refractive index of the surrounding medium can be tuned by proper choice of hematite thickness. IEEE