Simulation Of Light Scattering Research Articles

Simulation of Light Scattering and Imaging of Relay Wall in Non-Line-of-Sight Imaging

Simulation of Light Scattering and Imaging of Relay Wall in Non-Line-of-Sight Imaging

Light-Scattering Simulations from Spherical Bimetallic Core-Shell Nanoparticles.

Bimetallic nanoparticles show novel electronic, optical, catalytic or photocatalytic properties different from those of monometallic nanoparticles and arising from the combination of the properties related to the presence of two individual metals but also from the synergy between the two metals. In this regard, bimetallic nanoparticles find applications in several technological areas ranging from energy production and storage to sensing. Often, these applications are based on optical properties of the bimetallic nanoparticles, for example, in plasmonic solar cells or in surface-enhanced Raman spectroscopy-based sensors. Hence, in these applications, the specific interaction between the bimetallic nanoparticles and the electromagnetic radiation plays the dominant role: properties as localized surface plasmon resonances and light-scattering efficiency are determined by the structure and shape of the bimetallic nanoparticles. In particular, for example, concerning core-shell bimetallic nanoparticles, the optical properties are strongly affected by the core/shell sizes ratio. On the basis of these considerations, in the present work, the Mie theory is used to analyze the light-scattering properties of bimetallic core–shell spherical nanoparticles (Au/Ag, AuPd, AuPt, CuAg, PdPt). By changing the core and shell sizes, calculations of the intensity of scattered light from these nanoparticles are reported in polar diagrams, and a comparison between the resulting scattering efficiencies is carried out so as to set a general framework useful to design light-scattering-based devices for desired applications.

Rigorous light-scattering simulations of nanophase iron space-weathering effects on reflectance spectra of olivine grains

We present a multi-scale light-scattering model that is capable of simulating the reflectance spectra of a regolith layer. In particular, the model can be applied to a case where the regolith grains have varying amounts of nanophase inclusions due to space weathering of the material. As different simulation tools are employed for different size scales of the target geometry (roughly, nano-, micro-, and millimeter scales), the particle size effects, the surface reflections, and the volume scattering can all be properly accounted for. Our results with olivine grains and nanophase iron inclusions verify the role of the nanoinclusions in the reflectance spectra of space-weathered materials. Together with the simulation results, we give simplified explanations for the space-weathering effects based on light scattering, namely the decrease of albedo, the general increase of the red spectral slope, and the dampening of the spectral bands. We also consider the so-called ultraviolet bluing effect, and show how the change in the spectral slope over the ultraviolet–visual wavelengths is due to the decrease of reflectance in the visual wavelengths rather than the increase of reflectance in the ultraviolet part.

Numerical Simulation of Light Propagation and Scattering in Turbid Biological Media.

This article considers the processes of light propagation and scattering in biological tissues. The results obtained made it possible to estimate basic signal parameters and their dependence on various optical parameters with respect to the laser Doppler flowmeter and laser Doppler microscope. We also developed a new method to determine the indicatrix asymmetry of single and multiple light scattering by a suspension of oriented spheroidal particles that simulated erythrocytes in a shear flow. It was found that the angular dependence of the asymmetry index provides information on the shape and orientation of particles. In addition, we obtained single scattering indicatrices, which may improve the accuracy of computer simulation of light scattering by blood.

Optimizing the performance of CPML optical target for light-scattering simulations

An optical target constructed by modifying the convolutional perfectly matched layers (CPML) formulation is tested for applications in light-scattering simulations. The optical target is designed for finite-difference time-domain light-scattering simulations to eliminate and isolate impinging light. The performance of the optical target under different incident light and factors affecting the absorption efficiency is analyzed. Variations of the optical target geometry are tested for optimal absorption. Simulation results show that the absorption is most effective for normally impinging light; its absorption cross section can be effectively tuned by modifying the layers’ conductivity profile. In scattering simulations, the performance of such absorbing medium can effectively absorb incident light from arbitrary directions within a light-scattering simulation.

Determination of point-spread function of paper substrate based on light-scattering simulation.

The objective of this work was to establish the relationship between the calculated subsurface scattered-photon distribution and the mathematical quantity known as point-spread function (PSF). Photon distribution of subsurface scattered light was calculated using the Monte Carlo method developed for describing reflectance and opacity of paper and of images printed on paper. The obtained normalized photon distribution made it possible to separate optical and mechanical components of dot gain for the paper-ink system. In the presented method of obtaining the reflectance profile of a screen element, the PSF convolves with a modelled reflectance profile of that element. It was found that the PSF can be better approximated by means of the Lorentzian function when compared to the Gaussian profile that was used in the past research on this topic.

Study of electrophysical characteristics of blood formed elements using intracavity laser spectroscopy. I. Simulation of light-scattering by an ensemble of biological cells with complicated structures

Optical characteristics of an ensemble of arbitrarily oriented particles are studied in an optical cavity. The study is based on the self-consistent conjugation with respect to nonuniform optical cavities with the results of scattering by an ensemble of arbitrarily oriented spherical particles with different shapes and structures. A new electrodynamic model for the interaction of laser radiation with blood cells is constructed with allowance for the structure of cells for the prediction of optical properties in vivo.

GPU-accelerated T-matrix algorithm for light-scattering simulations

Modern graphical processing units (GPUs) have recently become a pervasive technology able to rapidly solve large parallel problems which previously required runs on clusters or supercomputers. In this paper we propose an effective strategy to parallelize the T-matrix method on GPUs in order to speed-up light scattering simulations. We have tackled two of the most computationally intensive scattering problems that are of interest in nano-optics: the scattering from an isolated non-axisymmetric particle and from an agglomerate of arbitrary shaped particles. We show that fully exploiting the GPU potential we can achieve more than 20 times (20×) acceleration over sequential execution in the investigated scenarios, opening exciting prospectives in the analysis and the design of optical nanostructures.

Geometrical-Optics Approximation for the Simulation of Light Scattering by Single-Nuclear Cell

According to the morphology of the single-nuclear cell, the eccentric-sphere (ES) model is proposed. The analytic expressions of amplitude function and phase function are revised base on the geometrical-optics approximation (GOA).The intensity distributing and phase distributing of the single-nuclear cell are also simulated by numerical calculation. The incident light orientation and the size of the nuclear on the impact of the backscattering have been discussed. After the analysis, we find that the model and the theory are much closer to the experimental fact compared with the single sphere model. These promote perfecting of the revised theory for inspection of real cell and provide a theory foundation for improving the measuring technique and identification technique of cells.

Sensitive light-scattering detection–magnetophoretic acceleration mass analysis of single microparticles in an atmosphere

Optically detected magnetophoretic acceleration mass analysis of an individual micro-particle in an atmosphere has been remarkably improved in sensitivity by using a reflective microscope objective, by which forward scattered light from a particle could be effectively collected. From the light-scattering simulation, the detection limit for the radius of a micro-particle was estimated to be smaller than 0.4μm, and about 60 times intensity enhancement was observed for a polystyrene particle with a radius of 2.8μm. For both paramagnetic and diamagnetic micro-particles, the mass magnetic susceptibility and the relaxation time could be determined without knowing any parameters of the particles. From the relaxation time, the mass of a particle was obtained if the radius or the density of the particle was known. For a test sample silica particles were used to adsorb paramagnetic dysprosium(III), the surface concentration of dysprosium(III) on a single particle could be successfully determined by use of this method.

Applicability of the discrete-dipole approximation to light-scattering simulations of large cosmic dust aggregates

Light-scattering properties of cosmic dust particles depend on the structure and composition of the particles. A common model assumption of cosmic dust particles that is consistent with observational data is to describe them as aggregates consisting of irregularly shaped, inhomogeneous, submicron-sized monomers. It is necessary for a study of their optical properties to apply a proper light-scattering theory, in which we can fully take this shape and structure of particles into account. Among currently available light-scattering theories, the discrete-dipole approximation (DDA) with the lattice dispersion relation (LDR) is the best method to simulate light scattering by aggregates of such complex structures. We investigate the accuracy of the LDR-DDA method with large aggregates consisting of spherically shaped, homogeneous, identical monomers of 0.1 µm in radius, for which rigorous solutions are known. The asymmetry parameter and single-scattering albedo of these aggregates are here computed with the LDR-DDA method as well as the superposition T-matrix method. We find that the conditions previously given in the literature to calculate cross sections of spherical particles within the accuracy of a few percent are also suitable for large aggregates. We discuss the required computer memory that restricts simulating the optical properties of the considered aggregates.

Light scattering by particulate media of irregularly shaped particles: laboratory measurements and numerical simulations

We present a light-scattering simulation based on geometrical optics to study the bidirectional reflectance of particulate media observed from laboratory measurements. The simulation model is built so that the arrangement of composing particles of the media and characteristics of the particles (i.e. size, irregularity of shape and refractive index) can be given as parameters. From the results of simulations and comparison with laboratory measurements, we have found the following: (1) The media of irregular-shaped particles show flatness in the angular change of the reflectance compared with those of more rounded particles. (2) The media of smaller particles with diameters of 150 μ m show brighter reflectance than those of 600 μ m , similarly as observed in laboratory measurements. (3) The reflectance in small ( < 30 ∘ ) and large ( > 120 ∘ ) phase angles increases with increasing surface porosity (i.e. enhancements of backscattering and forward scattering). The former can be ascribed to the first order of scattering in contrast with the latter to the first plus the second order of scattering, where the first order of scattering is the total sum of the scattered rays from the first particle hit by the incident ray, and the second means that from the second particle hit by the sub-rays from the first particle.

The inclusion-concentration measurement of suspensiondroplets based on Monte Carlo ray tracing

In this paper we analyse suspension dropletlight scattering with respect to measuring the size of the hostparticle and the inclusion concentration. The light-scattering simulations show significant changes in thescattering distribution of suspension droplets with differentinclusion concentrations. The evaluation reduces to only twoparameters, namely angular fringe spacing and the slope inthe scattering domain 30-70°. This method relieson the simulation of scattering with parameters such asthe refractive indices of the host and the inclusions and the size ofthe inclusions.

Monte Carlo multiple-scattering simulation and data correction in small-angle static light scattering

Monte Carlo methods usually employed for \ensuremath{\gamma}- and x-ray problems have recently been utilized for simulating multiple Rayleigh light scattering to all orders. Here a technique is discussed to separate the two-dimensional problem of generating the polar and azimuthal scattering angles into two independent one-dimensional samplings, thus increasing the computational efficiency. Although the method has quite a general applicability, this paper is focused on small-angle light-scattering simulations, and an artifice is introduced which reduces the inherent poor efficiency of the polar angle sampling in conjunction with differential scattering cross sections that are sharply peaked in the forward direction. As a test, the technique was used to correct two sets of experimental data affected by multiple scattering. Microporous membrane filters under quasi-index-matching conditions were investigated, and two stacks of different thickness were used. While the raw data are of course appreciably different for different sample thicknesses, the corrected scattered intensity distributions are the same, thus providing evidence of the method effectiveness in retrieving the single-scattered intensity distributions.

Nature of light scattering in dental enamel and dentin at visible and near-infrared wavelengths

The light-scattering properties of dental enamel and dentin were measured at 543, 632, and 1053 nm. Angularly resolved scattering distributions for these materials were measured from 0° to 180° using a rotating goniometer. Surface scattering was minimized by immersing the samples in an index-matching bath. The scattering and absorption coefficients and the scattering phase function were deduced by comparing the measured scattering data with angularly resolved Monte Carlo light-scattering simulations. Enamel and dentin were best represented by a linear combination of a highly forward-peaked Henyey-Greenstein (HG) phase function and an isotropic phase function. Enamel weakly scatters light between 543 nm and 1.06 µm, with the scattering coefficient (µ(s)) ranging from µ(s) = 15 to 105 cm(-1). The phase function is a combination of a HG function with g = 0.96 and a 30-60% isotropic phase function. For enamel, absorption is negligible. Dentin scatters strongly in the visible and near IR (µ(s)≅260 cm(-1)) and absorbs weakly (µ(a) ≅ 4 cm(-1)). The scattering phase function for dentin is described by a HG function with g = 0.93 and a very weak isotropic scattering component (˜ 2%).

Use of tabulated cumulative density functions to generate pseudorandom numbers obeying specific distributions for Monte Carlo simulations

A new method for the generation of pseudorandom numbers, which obey a specific statistical distribution, is presented. As an example the generation of the scattering angle θ for Monte Carlo light-scattering simulations is shown, using real, peaked, scattering phase functions.

Simulation of Light Scattering and Determination of the MTF of Positive Photoresists using the Monte Carlo Method

Simulation of Light Scattering and Determination of the MTF of Positive Photoresists using the Monte Carlo Method