Rigorous theoretical framework for particle sizing in turbid colloids using light refraction

Garcı́a-Valenzuela, Augusto; Barrera, Rubén G.; Gutiérrez-Reyes, Edahí

doi:10.1364/oe.16.019741

Cited by 25 publications

(19 citation statements)

References 19 publications

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“…The coherent component corresponds to the average of the electromagnetic fields over all the permitted microscopic configurations of the system, whereas the diffuse component relates to the fluctuations of the electromagnetic fields around its average [1,5,[14][15][16]19,20,25]. When scattering is strong the coherent component decays rapidly within the bulk of the material and all is converted to diffuse light or absorbed.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…When absorption by the material is small, most of the energy flux is carried by the diffuse component. The effective RI assigned to the coherent component of light has been investigated in recent years [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], and its nonlocal nature has been established [19,25]. However, as already said the effective RI seen by diffuse light has been barely investigated, and the only reference reporting efforts in the past that helps address this question is that of Meeten and North [6].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Refractive index measurement of turbid media by transmission of backscattered light near the critical angle

Contreras-Tello

Garcı́a-Valenzuela

2014

Appl. Opt.

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We investigate experimentally the determination of the effective refractive index (RI) of a turbid particle suspension from the angle dependence of light scattered by the particles and then transmitted into a transparent prism of higher RI. We assembled a versatile experimental device that may be recognized as an Abbe-type refractometer in which the sample is illuminated from the prism side and use it to measure the intensity profile of diffuse light refracted into the prism around the critical angle. By fitting a recently proposed theoretical model we extract the complex RI of turbid suspensions of particles from the measured intensity profiles. We show that the real part of the effective RI is readily obtained with good precision regardless of how the sample is illuminated, whereas obtaining the imaginary part is done with less precision but nevertheless useful measurements can be obtained. The effective RI obtained with this method compares very well with the so-called van de Hulst effective RI and the one derived from Keller's model of the effective propagation constant.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Theoretical Backgroundmentioning

confidence: 99%

Refractive index measurement of turbid media by transmission of backscattered light near the critical angle

Contreras-Tello

Garcı́a-Valenzuela

2014

Appl. Opt.

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“…Direct computer solutions of the MMEs for morphologically complex objects can be quite time-consuming and in many cases impracticable. As a consequence, there has been a widespread use of phenomenological so-called effective-medium rules intended to drastically simplify the computation (see [72][73][74][75][76][77][78][192][193][194][195][196][197][198][199] and references therein). Implicitly, the main idea of an effective-object approximation (EOA) (more commonly known as an effective-medium approximation, or EMA) is to replace a morphologically complex object, either fixed or randomly varying in time, by a much simpler "effective" object possessing essentially the same scattering properties.…”

Section: Effective-object Methodologymentioning

confidence: 99%

“…Note that we intentionally defined the three EOAs in terms of the linear operators Î and scâ ℑ acting on an optical observable rather than on the macroscopic field vectors (of course these definitions can be generalized to include types of optical observables other than the Poynting-Stokes tensor). Traditionally, however, EMAs have been introduced with the purpose of replicating the average macroscopic field vectors rather than specific optical observables [72][73][74][75][76][77][78][192][193][194][195][196][197][198][199]. In other words, a semi-stochastic EOA would normally be introduced as a recipe for replacing a stochastic morphologically complex scattering object by a fixed simple "effective" object such that in Eq.…”

Section: Effective-object Methodologymentioning

confidence: 99%

First-principles modeling of electromagnetic scattering by discrete and discretely heterogeneous random media

et al. 2016

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A discrete random medium is an object in the form of a finite volume of a vacuum or a homogeneous material medium filled with quasi-randomly and quasi-uniformly distributed discrete macroscopic impurities called small particles. Such objects are ubiquitous in natural and artificial environments. They are often characterized by analyzing theoretically the results of laboratory, in situ, or remote-sensing measurements of the scattering of light and other electromagnetic radiation. Electromagnetic scattering and absorption by particles can also affect the energy budget of a discrete random medium and hence various ambient physical and chemical processes. In either case electromagnetic scattering must be modeled in terms of appropriate optical observables, i.e., quadratic or bilinear forms in the field that quantify the reading of a relevant optical instrument or the electromagnetic energy budget. It is generally believed that time-harmonic Maxwell's equations can accurately describe elastic electromagnetic scattering by macroscopic particulate media that change in time much more slowly than the incident electromagnetic field. However, direct solutions of these equations for discrete random media had been impracticable until quite recently. This has led to a widespread use of various phenomenological approaches in situations when their very applicability can be questioned. Recently, however, a new branch of physical optics has emerged wherein electromagnetic scattering by discrete and discretely heterogeneous random media is modeled directly by using analytical or numerically exact computer solutions of the Maxwell equations. Therefore, the main objective of this Report is to formulate the general theoretical framework of electromagnetic scattering by discrete random media rooted in the MaxwellLorentz electromagnetics and discuss its immediate analytical and numerical consequences. Starting from the microscopic Maxwell-Lorentz equations, we trace the development of the firstprinciples formalism enabling accurate calculations of monochromatic and quasi-monochromatic scattering by static and randomly varying multiparticle groups. We illustrate how this general framework can be coupled with state-of-the-art computer solvers of the Maxwell equations and applied to direct modeling of electromagnetic scattering by representative random multi-particle groups with arbitrary packing densities. This first-principles modeling yields general physical insights unavailable with phenomenological approaches. We discuss how the first-order-scattering approximation, the radiative transfer theory, and the theory of weak localization of electromagnetic waves can be derived as immediate corollaries of the Maxwell equations for very specific and well-defined kinds of particulate medium. These recent developments confirm the mesoscopic origin of the radiative transfer, weak localization, and effective-medium regimes and help evaluate the numerical accuracy of widely used approximate modeling methodologies.

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“…However, in contrast to Refs. 16,17, and 18 where a small subset of the reflectance curve was focused on and previous works 5,14,15,20 where just ∼20 data points were fitted, here we fit the entire reflectance curve comprising ∼1000 data points. In further contrast to previous works 5, [19][20][21] we employ no other fitting parameters besides the two variables we seek to determine-the real and imaginary parts of the refractive index-thus avoiding ambiguity in the extracted values owing to overfitting.…”

Section: Introductionmentioning

confidence: 99%

Accuratein situmeasurement of complex refractive index and particle size in intralipid emulsions

et al. 2013

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Abstract. A first accurate measurement of the complex refractive index in an intralipid emulsion is demonstrated, and thereby the average scatterer particle size using standard Mie scattering calculations is extracted. Our method is based on measurement and modeling of the reflectance of a divergent laser beam from the sample surface. In the absence of any definitive reference data for the complex refractive index or particle size in highly turbid intralipid emulsions, we base our claim of accuracy on the fact that our work offers several critically important advantages over previously reported attempts. First, our measurements are in situ in the sense that they do not require any sample dilution, thus eliminating dilution errors. Second, our theoretical model does not employ any fitting parameters other than the two quantities we seek to determine, i.e., the real and imaginary parts of the refractive index, thus eliminating ambiguities arising from multiple extraneous fitting parameters. Third, we fit the entire reflectanceversus-incident-angle data curve instead of focusing on only the critical angle region, which is just a small subset of the data. Finally, despite our use of highly scattering opaque samples, our experiment uniquely satisfies a key assumption behind the Mie scattering formalism, namely, no multiple scattering occurs. Further proof of our method's validity is given by the fact that our measured particle size finds good agreement with the value obtained by dynamic light scattering. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Rigorous theoretical framework for particle sizing in turbid colloids using light refraction

Cited by 25 publications

References 19 publications

Refractive index measurement of turbid media by transmission of backscattered light near the critical angle

Refractive index measurement of turbid media by transmission of backscattered light near the critical angle

First-principles modeling of electromagnetic scattering by discrete and discretely heterogeneous random media

Accuratein situmeasurement of complex refractive index and particle size in intralipid emulsions

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