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Publications

Publications by Maria Inês Carvalho

2013

Lightons: Phonons with light

Authors
Silva, NA; Carvalho, MI; Guerreiro, A;

Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS

Abstract
Spatial solitons are robust localized nonlinear waves that are able to propagate without significant changes to their structure. Most of the proposal of the application of solitons uses them to transmit and process information in optical fibers and optical circuits. In the later the solitons can be guided through different paths by presetting some soliton characteristics (such as the phase), and even using some solitons to control the path of other pulses. In this paper, we use these properties of optical spatial solitons in a cubic nonlinear media to have lightons: phonon-like oscillations of a chain of solitonic light pulses. Conceptually, this work aims to explore the dual nature of solitons as a particle-like wave, by considering the displacement wave of solitons in a 1-dimensional chain.

2018

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

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

Publication
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.

2013

Spatial soliton dynamics in cubic-quintic media

Authors
Silva, NA; Carvalho, MI; Guerreiro, A;

Publication
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS

Abstract
In this paper we address soliton-soliton interactions in a nonlinear cubic-quintic optic media, using for that purpose numerical methods and high performance graphics processor unit (GPU) computing. We describe an implementation of GPU-based computational simulations of the generalized Nonlinear Schrodinger Equation, obtaining simulations more than 40 times faster relative to CPU-based simulations, especially in the multidimensional case. We focus our attention in the study of soliton collisions and scattering phenomena that, offering the possibility of steering light with light, open a path towards future optical devices.

2013

The characteristic time of glucose diffusion measured for muscle tissue at optical clearing

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

Publication
LASER PHYSICS

Abstract
The study of agent diffusion in biological tissues is very important to understand and characterize the optical clearing effects and mechanisms involved: tissue dehydration and refractive index matching. From measurements made to study the optical clearing, it is obvious that light scattering is reduced and that the optical properties of the tissue are controlled in the process. On the other hand, optical measurements do not allow direct determination of the diffusion properties of the agent in the tissue and some calculations are necessary to estimate those properties. This fact is imposed by the occurrence of two fluxes at optical clearing: water typically directed out of and agent directed into the tissue. When the water content in the immersion solution is approximately the same as the free water content of the tissue, a balance is established for water and the agent flux dominates. To prove this concept experimentally, we have measured the collimated transmittance of skeletal muscle samples under treatment with aqueous solutions containing different concentrations of glucose. After estimating the mean diffusion time values for each of the treatments we have represented those values as a function of glucose concentration in solution. Such a representation presents a maximum diffusion time for a water content in solution equal to the tissue free water content. Such a maximum represents the real diffusion time of glucose in the muscle and with this value we could calculate the corresponding diffusion coefficient.

2017

Plain and oscillatory solitons of the cubic complex Ginzburg-Landau equation with nonlinear gradient terms

Authors
Facao, M; Carvalho, MI;

Publication
PHYSICAL REVIEW E

Abstract
In this work, we present parameter regions for the existence of stable plain solitons of the cubic complex Ginzburg-Landau equation (CGLE) with higher-order terms associated with a fourth-order expansion. Using a perturbation approach around the nonlinear Schrdinger equation soliton and a full numerical analysis that solves an ordinary differential equation for the soliton profiles and using the Evans method in the search for unstable eigenvalues, we have found that the minimum equation allowing these stable solitons is the cubic CGLE plus a term known in optics as Raman-delayed response, which is responsible for the redshift of the spectrum. The other favorable term for the occurrence of stable solitons is a term that represents the increase of nonlinear gain with higher frequencies. At the stability boundary, a bifurcation occurs giving rise to stable oscillatory solitons for higher values of the nonlinear gain. These oscillations can have very high amplitudes, with the pulse energy changing more than two orders of magnitude in a period, and they can even exhibit more complex dynamics such as period-doubling.

2014

Experimental Setup for Electromagnetically Induced Transparency Observation in Hollow-Core Fibers

Authors
Tiburcio, BD; Fernandes, GM; Monteiro, JM; Rodrigues, S; Carvalho, MI; Facao, M; Ferreira, M; Pinto, AN;

Publication
SECOND INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS

Abstract
We developed a system to investigate resonant nonlinear optical interactions in acetylene molecules, confined in a hollow-core photonic crystal fiber (HC-PCF), using light injection through a low-loss splice from one end of the fiber, allowing us to work at low power. Electromagnetically induced transparency (EIT) was observed in the 1500 nm telecommunications window.

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