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Publications

Publications by CTM

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.

2013

Comparison between optical measurements made from natural and frozen samples at optical clearing

Authors
Oliveira, L; Carvalho, MI; Nogueira, E; Tuchin, VV;

Publication
SARATOV FALL MEETING 2012: OPTICAL TECHNOLOGIES IN BIOPHYSICS AND MEDICINE XIV; AND LASER PHYSICS AND PHOTONICS XIV

Abstract
To determine the differences between the optical clearing effects created by ethylene glycol in fresh and frozen samples, we have performed several measurements from samples in both conditions. Fresh samples were used after animal sacrifice and frozen samples were kept at -20 degrees C for 72 hours. The different measurements performed with samples from both cases were total transmittance, collimated transmittance, total reflectance and specular reflectance. Considering, for instance, collimated transmittance measurements, we have verified that the spectra measured from both samples before adding the solution present different levels of collimated transmittance. The time-dependence evolution of the collimated transmittance spectrum is similar between both cases of samples, but since they present different levels of "natural" transmittance, the optical clearing effect is observed at different levels if we compare between fresh and frozen samples.

2013

Continuous wave supercontinuum generation pumped in the normal group velocity dispersion regime on a highly nonlinear fiber

Authors
Facao, M; Carvalho, MI; Fernandes, GM; Rocha, AM; Pinto, AN;

Publication
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS

Abstract
We have obtained spectral broadening by pumping a nonmicrostructured highly nonlinear fiber with a continuous wave signal from a Raman fiber laser. The experiment was simulated using a generalized Schrodinger equation containing the actual Raman response of the fiber as calculated from the experimental Raman gain. A different input-noise model, that reproduces well the power spectral density of the laser, was used and compared with others previously proposed. (C) 2013 Optical Society of America

2013

Accelerating solitons in gas-filled hollow-core photonic crystal fibers

Authors
Facao, M; Carvalho, MI; Almeida, P;

Publication
PHYSICAL REVIEW A

Abstract
We found the self-similar solitary solutions of a recently proposed model for the propagation of pulses in gas-filled hollow-core photonic crystal fibers that includes a plasma induced nonlinearity. As anticipated for a simpler model and using a perturbation analysis, there are indeed stationary solitary waves that accelerate and self-shift to higher frequencies. However, if the plasma nonlinearity strength is large or the pulse amplitudes are small, the solutions have distinguished long tails and decay as they propagate.

2013

OPTICAL MEASUREMENTS OF RAT MUSCLE SAMPLES UNDER TREATMENT WITH ETHYLENE GLYCOL AND GLUCOSE

Authors
Oliveira, L; Carvalho, MI; Nogueira, E; Tuchin, VV;

Publication
JOURNAL OF INNOVATIVE OPTICAL HEALTH SCIENCES

Abstract
With the objective to study the variation of optical properties of rat muscle during optical clearing, we have performed a set of optical measurements from that kind of tissue. The measurements performed were total transmittance, collimated transmittance, specular reflectance and total reflectance. This set of measurements is sufficient to determine diffuse reflectance and absorbance of the sample, also necessary to estimate the optical properties. All the performed measurements and calculated quantities will be used later in inverse Monte Carlo (IMC) simulations to determine the evolution of the optical properties of muscle during treatments with ethylene glycol and glucose. The results obtained with the measurements already provide some information about the optical clearing treatments applied to the muscle and translate the mechanisms of turning the tissue more transparent and sequence of regimes of optical clearing.

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