Search results for "Light propagation"
showing 9 items of 9 documents
Exact analytic expressions for electromagnetic propagation and optical nonlinear generation in finite one-dimensional periodic multilayers.
2004
Translation Matrix Formalism has been used to find an exact analytic solution for linear light propagation in a finite one-dimensional (1D) periodic stratified structure. This modal approach allows to derive a closed formula for the electric field in every point of the structure, by simply imposing a convenient form for the boundary conditions. We show how to apply this result to Second Harmonic Generation (SHG) in the undepleted pump regime.
Light Propagation in Heterogeneous Opal-Based Photonic Crystals
2006
Ballistic light propagation in the heterogeneous photonic crystals based on the thin triple-film opal have been studied in the wavelength range of low order photonic bandgaps. Since the scattered light experiences the diffraction attenuation, the spectra and the angle diagrams of the transmitted and forward scattered light have been used to identify the effect of heterostructuring.
Vectorial Kerr-cavity solitons.
2000
It is shown that a Kerr cavity with different losses for the two polarization components of the field can support both dark and bright cavity solitons (CS’s). A parametrically driven Ginzburg–Landau equation is shown to describe the system for large-cavity anisotropy. In one transverse dimension the nonlinear dynamics of the bright CS’s is numerically investigated.
Development of an imaging system dedicated to the acquisition analysis and multispectral characterisation of skin lesion
2011
Visual evaluation of cutaneous lesions is the analysis the most commonly performedby dermatologists. This diagnostic is mainly done by naked eye and is based on criterionsuch as the size, shape, symmetry but principally on colour of the lesions. However, thisanalysis is subjective because it depends on the practician experience and the acquisitionconditions. We propose in this dissertation (1) the development of a multispectralcamera specifically dedicated for dermatological use. This device is based on a filterwheel composed of interferential filters and a neural network-based algorithm, generatinga hyperspectral cube of cutaneous data. This setting combines advantage of both spectrophotom…
Measurement of haemodynamics of exercising and non-exercising vastus lateralis muscle with hybrid diffuse optics
2016
We present simultaneous diffuse correlation spectroscopy (DCS) and time resolved spectroscopy (TR NIRS) measurements on exercising and non-exercising vastus lateralis muscle. We discuss the results at two different exercise levels.
3D multispectral light propagation model for subcutaneous veins imaging
2008
In this paper, we describe a new 3D light propagation model aimed at understanding the effects of various physiological properties on subcutaneous vein imaging. In particular, we build upon the well known MCML (Monte Carlo Multi Layer) code and present a tissue model that improves upon the current state-of-the-art by: incorporating physiological variation, such as melanin concentration, fat content, and layer thickness; including veins of varying depth and diameter; using curved surfaces from real arm shapes; and modeling the vessel wall interface. We describe our model, present results from the Monte Carlo modeling, and compare these results with those obtained with other Monte Carlo metho…
Assessing sensory versus optogenetic network activation by combining (o)fMRI with optical Ca2+ recordings
2016
Encoding of sensory inputs in the cortex is characterized by sparse neuronal network activation. Optogenetic stimulation has previously been combined with fMRI (ofMRI) to probe functional networks. However, for a quantitative optogenetic probing of sensory-driven sparse network activation, the level of similarity between sensory and optogenetic network activation needs to be explored. Here, we complement ofMRI with optic fiber-based population Ca2+ recordings for a region-specific readout of neuronal spiking activity in rat brain. Comparing Ca2+ responses to the blood oxygenation level-dependent signal upon sensory stimulation with increasing frequencies showed adaptation of Ca2+ transient…
Twisted-Light-Ion Interaction: The Role of Longitudinal Fields.
2017
The propagation of light beams is well described using the paraxial approximation, where field components along the propagation direction are usually neglected. For strongly inhomogeneous or shaped light fields, however, this approximation may fail, leading to intriguing variations of the light-matter interaction. This is the case of twisted light having opposite orbital and spin angular momenta. We compare experimental data for the excitation of a quadrupole transition in a single trapped $^{40}$Ca$^+$ ion by Schmiegelow et al, Nat.\ Comm.\ 7, 12998 (2016), with a complete model where longitudinal components of the electric field are taken into account. Our model matches the experimental d…
Light propagation in triple-film hetero-opals
2005
Spectra of transmitted and forward scattered light of single opal films and triple-film hetero-opals have been compared. The presence of an intermediate film in hetero-opal results in an anomalous increase of the scattered light intensity and in the change of the mainly ballistic light propagation regime to the mainly diffusive one in the frequency range of the photonic bandgap defect state.