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Publicações

Publicações por PHT

2023

1st Spring Biophotonics Conference in Porto

Autores
Oliveira, LM; Meglinski, I; Tuchin, VV;

Publicação
JOURNAL OF BIOPHOTONICS

Abstract
[No abstract available]

2023

Erbium-doped fiber ring cavity for the measurement of refractive index variations

Autores
Perez Herrera, RA; Soares, L; Novais, S; Frazão, O; Silva, S;

Publicação
Proceedings of SPIE - The International Society for Optical Engineering

Abstract

2023

Fast calculation of spectral optical properties and pigment content detection in human normal and pathological kidney

Autores
Botelho, AR; Silva, HF; Martins, IS; Carneiro, IC; Carvalho, SD; Henrique, RM; Tuchin, VV; Oliveira, LM;

Publicação
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

Abstract
A fast calculation method was used to obtain the spectral optical properties of human normal and pathological (chromophobe renal cell carcinoma) kidney tissues. Using total transmittance, total reflectance and collimated transmittance spectra acquired from ex vivo kidney samples, the spectral optical properties of both tissues, namely the absorption, the scattering and the reduced scattering coefficients, as well as the scattering anisotropy, dispersion and light penetration depth, were calculated between 200 and 1000 nm. Analysis of the mean absorption coefficient spectra of the kidney tissues showed that both contain melanin and lipofuscin, and that 83 % of the melanin in the normal kidney converts into lipofuscin in the pathological kidney.

2023

Vernier Effect in a Compact Strain Sensor Based on Fiber Loop Mirrors Using a 3 x 3 Coupler

Autores
Soares, B; Silva, S; Ribeiro, P; Frazao, O;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
In this letter, a new configuration based on two fiber loop mirrors in series using a 3x3 coupler is demonstrated. This configuration is compact and can explore the Vernier effect. The results obtained were a sensitivity of 74.9 +/- 0.2 pm/ mu epsilon for the Vernier envelope and 6.41 +/- 0.01 pm/mu epsilon for the Vernier carrier. These results were compared to the sensitivity of the setup using only one fiber loop mirror interferometer, obtaining 14.41 +/- 0.01 pm/mu epsilon. This means a magnification factor of 5.2 for the Vernier envelope. Theoretical treatment of the system was carried out, using Jones matrix calculus, and the subsequent simulation results are also presented, having obtained good agreement with the experimental data.

2023

Fiber Loop Mirror Based on Optical Fiber Circulator for Sensing Applications

Autores
Robalinho, P; Soares, B; Lobo, A; Silva, S; Frazao, O;

Publicação
SENSORS

Abstract
In this paper, a different Fiber Loop Mirror (FLM) configuration with two circulators is presented. This configuration is demonstrated and characterized for sensing applications. This new design concept was used for strain and torsion discrimination. For strain measurement, the interference fringe displacement has a sensitivity of (0.576 +/- 0.009) pm.mu epsilon(-1). When the FFT (Fast Fourier Transformer) is calculated and the frequency shift and signal amplitude are monitored, the sensitivities are (-2.1 +/- 0.3) x 10(-4) nm(-1) mu epsilon(-1) and (4.9 +/- 0.3) x 10(-7) mu epsilon(-1), respectively. For the characterization in torsion, an FFT peaks variation of (-2.177 +/- 0.002) x 10(-12) nm(-1)/degrees and an amplitude variation of (1.02 +/- 0.06) x 10(-3)/degrees are achieved. This configuration allows the use of a wide range of fiber lengths and with different refractive indices for controlling the free spectral range (FSR) and achieving refractive index differences, i.e., birefringence, higher than 10(-2), which is essential for the development of high sensitivity physical parameter sensors, such as operating on the Vernier effect. Furthermore, this FLM configuration allows the system to be balanced, which is not possible with traditional FLMs.

2023

Measurement of Paracetamol Concentration Using an Erbium-Doped Fiber Ring Cavity

Autores
Soares, L; Perez Herrera, RA; Novais, S; Ferreira, A; Silva, S; Frazao, O;

Publicação
PHOTONICS

Abstract
Process Analytical Technology (PAT) has been increasingly used in the pharmaceutical industry to monitor essential parameters in real-time during pharmaceutical processes. The concentration of Active Pharmaceutical Ingredients (APIs), such as paracetamol, is one of these parameters, and controlling its variations allows for optimization of the production process. In this study, a refractometric sensor, implemented by an interrogation system based on an Erbium-Doped Fiber Ring Cavity (EDFRC), was presented and experimentally demonstrated. The Cavity Ring proposed included a 1 x 3 coupler. One port of the coupler was used to increase the optical power of the system through a Fiber Bragg Grating (FBG), and the other two ports were used as sensing head and reference. The sensor detected variations of paracetamol concentration with a sensitivity of [(-1.00 +/- 0.05) x 10(-3)] nW/(g/kg) and a resolution of 5.53 g/kg. The results demonstrate the potential of this technology as a possible non-invasive PAT tool.

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