Publications

Publications by Paulo Caldas

2010

<title>Characterization of nanolayer LPG refractometer according surrounding refractive index</title>

Authors
Simões, E; Abe, I; Oliveira, J; Pinto, JL; Caldas, P; Frazão, O;

Publication
Fourth European Workshop on Optical Fibre Sensors

Abstract

2010

<title>20-mW 70-nm bandwidth ASE fibre optic source at 1060-nm wavelength region for optical coherence tomography</title>

Authors
Trifanov, I; Caldas, P; Neagu, L; Romero, R; Berendt, MO; Salcedo, JR; Podoleanu, AG; Lobo Ribeiro, AB;

Publication
Fiber Lasers VII: Technology, Systems, and Applications

Abstract

2011

<title>Comparative study of different parameters of fibre Bragg gratings and long period gratings sensors for high-temperature measurements</title>

Authors
Melo, LB; Ângelo, N; Aberto, N; Marques, C; Monteiro, J; Rego, G; Caldas, P; Nogueira, R;

Publication
International Conference on Applications of Optics and Photonics

Abstract

2012

Fibre Sensing System Based on Long-Period Gratings for Monitoring Aqueous Environments

Authors
Silva, C; P. Coelho, JM; Caldas, P; Jorge, P;

Publication
Fiber Optic Sensors

Abstract

2011

Characterization of optical fiber long period grating refractometer with nanocoating

Authors
Simoes, E; Abe, I; Oliveira, J; Frazao, O; Caldas, P; Pinto, JL;

Publication
SENSORS AND ACTUATORS B-CHEMICAL

Abstract
In this work is studied the response of optical fiber long period grating (LPG) to changes of the refractive index of the external media relatively to variations of wavelength and in transmission. The response of the LPG to refractive index greater and lesser than to cladding is investigated. A nanolayer was deposited onto the fiber to increase the sensitivity of the LPG to refractive index of the external media higher than cladding. The film modifies the rates of effective modes of cladding, thus improving the response of the changes in the refractive index of the external media higher than that in the refractive index of the cladding (n(cl) approximate to 1.457). The Langmuir-Blodgett technique was used for the deposition of the nanolayer.

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2011

Combined Neodymium-Ytterbium-Doped ASE Fiber-Optic Source for Optical Coherence Tomography Applications

Authors
Trifanov, I; Caldas, P; Neagu, L; Romero, R; Berendt, MO; Salcedo, JAR; Podoleanu, AG; Lobo Ribeiro, ABL;

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
Optical coherence tomography (OCT) imaging at the 1060-nm region proved to be a successful alternative in ophthalmology not only for resolving intraretinal layers, but also for enabling sufficient penetration to monitor the subretinal vasculature in the choroid when compared to most commonly used OCT imaging systems at the 800-nm region. To encourage further clinical research at this particular wavelength, we have developed a compact fiber-optic source based on amplified spontaneous emission (ASE) centered at similar to 1060 nm with similar to 70-nm spectral bandwidth at full-width at half-maximum and output power > 20 mW. Our approach is based on a combination of slightly shifted ASE emission spectra from a combination of Neodymium- and Ytterbium-doped fibers. Spectral shaping and power optimization have been achieved using in-fiber filtering schemes. We have tested the performance of the source in an OCT system optimized for this wavelength.

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