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Detalhes

Detalhes

003
Publicações

2020

Modelling and simulation of electromagnetically induced transparency in hollow-core microstructured optical fibres

Autores
Rodrigues, SMG; Facao, M; Ines Carvalho, MI; Ferreira, MFS;

Publicação
OPTICS COMMUNICATIONS

Abstract
We study the electromagnetically induced transparency (EIT) phenomenon in a hollow-core fibre filled with rubidium gas. We analyse the impact of the guiding effect and of the temperature on the properties of the EIT phenomenon. The refractive index felt by the probe laser is found to vary due to the radial dependence of the fibre mode field at the pump frequency. Several results are presented for the transmission, dispersion, and group velocity of the probe field, considering both the free propagation regime and the guided propagation along the hollow-core fibre. We note that the EIT occurring in a waveguide has a great potential for practical applications since it can be controlled by adjusting the gas and the fibre properties.

2019

Estimation of atmospheric turbulence parameters from Shack-Hartmann wavefront sensor measurements

Autores
Andrade, PP; Garcia, PJV; Correia, CM; Kolb, J; Carvalho, MI;

Publicação
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Abstract
The estimation of atmospheric turbulence parameters is of relevance for the following: (a) site evaluation and characterization; (b) prediction of the point spread function; (c) live assessment of error budgets and optimization of adaptive optics performance; (d) optimization of fringe trackers for long baseline optical interferometry. The ubiquitous deployment of Shack-Hartmann wavefront sensors in large telescopes makes them central for atmospheric turbulence parameter estimation via adaptive optics telemetry. Several methods for the estimation of the Fried parameter and outer scale have been developed, most of which are based on the fitting of Zernike polynomial coefficient variances reconstructed from the telemetry. The non-orthogonality of Zernike polynomial derivatives introduces modal cross coupling, which affects the variances. Furthermore, the finite resolution of the sensor introduces aliasing. In this article the impact of these effects on atmospheric turbulence parameter estimation is addressed with simulations. It is found that cross-coupling is the dominant bias. An iterative algorithm to overcome it is presented. Simulations are conducted for typical ranges of the outer scale (4-32 m), Fried parameter (10 cm) and noise in the variances (signal-to-noise ratio of 10 and above). It is found that, using the algorithm, both parameters are recovered with sub-per cent accuracy.

2019

Dissipative solitons for generalizations of the cubic complex Ginzburg-Landau equation

Autores
Carvalho, MI; Facao, M;

Publicação
PHYSICAL REVIEW E

Abstract
We found stable soliton solutions for two generalizations of the cubic complex Ginzburg-Landau equation, namely, one that includes the term that, in optics, represents a delayed response of the nonlinear gain and the other including the self-steepening term, also in the optical context. These solutions do not require the presence of the delayed response of the nonlinear refractive index, such that, they exist regardless of the term previously considered essential for stabilization. The existence of these solitons was predicted by a perturbation approach, and then confirmed by solving the ordinary differential equations, resulting from a similarity reduction, and also by applying a linear stability analysis. We found that these solitons exist for a large region of the parameter space and possess very asymmetric amplitude profiles as well as a complicated chirp characteristic.

2018

Evaluation of SAR induced by a planar inverted-F antenna based on a realistic human model

Autores
Vieira, VF; Pessoa, LM; Carvalho, MI;

Publicação
IFMBE Proceedings

Abstract
In this paper the absorption by the human body of electromagnetic (EM) radiation generated by a Planar Inverted-F Antenna (PIFA) from a modern mobile phone is investigated through the evaluation of the Specific Absorption Rate (SAR) in head, brain and hand regions using Sim4Life (S4L) and a realistic anatomical model. Several scenarios were evaluated, by varying the distance between the antenna and the head, the feeder position and the orientation of the antenna. The effect of the presence of the hand was also studied and, finally, different communication bands were considered. The main results show that the presence of the hand is determinant to reduce SAR on head and brain, while bottom orientations of the antenna reduce the SAR on the brain, but increase the SAR in other tissues. © Springer Nature Singapore Pte Ltd. 2018.

2018

Skeletal muscle dispersion (400-1000?nm) and kinetics at optical clearing

Autores
Oliveira, LM; Carvalho, MI; Nogueira, EM; Tuchin, VV;

Publicação
Journal of Biophotonics

Abstract

Teses
supervisionadas

2019

Superfície de adaptação baseada em metamateriais para imagiologia por microondas

Autor
Ana Luísa Jorge Anes

Instituição
UP-FEUP

2019

Optical characterization of atmospheric turbulence

Autor
Paulo Alexandre Paiva de Andrade

Instituição
UP-FEUP

2018

Superfície de adaptação baseada em metamateriais para imagiologia por

Autor
Ana Luísa Jorge Anes

Instituição
UP-FEUP

2017

Optical characterization of atmospheric turbulence

Autor
Paulo Alexandre Paiva de Andrade

Instituição
UP-FEUP

2017

Effect of electromagnetic fields induced by mobile devices in the human brain

Autor
Vânia Filomena Madureira Vieira

Instituição
UP-FEUP