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In dense multiple scattering media, optical fields evolve through both homogeneous and evanescent waves. New regimes of light transport emerge because of the near-field coupling between individual scattering centers at mesoscopic scales. We present a novel propagation model that is developed in terms of measurable far- and near-field scattering cross sections. Our quantitative description explains the increase of total transmission in dense scattering media and its accuracy is established through both full-scale numerical calculations and enhanced backscattering experiments. [ABSTRACT FROM AUTHOR]

Transparent glass composites containing nonlinear optical (NLO) and luminescent crystals are of significant interest for the optical materials science in spire of a lot of difficulties to synthesize high-quality NLO composites: refractive index and density matching! of glass matrix and crystal, controlled chemical interaction between them, absence of crystal aggregation, cords, bubbles, etc. Low density and refractive index, high second harmonic generation (SHG) activity, rather a high melting point allow to refer KNbSi2O7 ferroelectric to a promising candidate for using in the NLO glass composite technology. Manifestation of NLO properties of crystals in glass composites is established to depend drastically on glass matrix composition. During re-melting lead containing glasses react chemically with KNbSi2O7 forming pyrochlore Pb2Nb2O7 which is dissolved gradually up to nano-scaled state exhibiting moderate SHG efficiency by analogy with nanostructured glasses because of space modulation of polarizability originated from nano-sized inhomogeneities enriched with Pb and Nb. Using of TeO2-based glasses permits to match reft active indexes of glass matrix and crystal, reduce glass melting temperature and fabricate transparent composites containing micron and sub-micron crystals with high second harmonic generation activity. [ABSTRACT FROM AUTHOR]

Transparent glass composites containing nonlinear optical (NLO) and luminescent crystals are of significant interest for the optical materials science in spire of a lot of difficulties to synthesize high-quality NLO composites: refractive index and density matching! of glass matrix and crystal, controlled chemical interaction between them, absence of crystal aggregation, cords, bubbles, etc. Low density and refractive index, high second harmonic generation (SHG) activity, rather a high melting point allow to refer KNbSi2O7 ferroelectric to a promising candidate for using in the NLO glass composite technology. Manifestation of NLO properties of crystals in glass composites is established to depend drastically on glass matrix composition. During re-melting lead containing glasses react chemically with KNbSi2O7 forming pyrochlore Pb2Nb2O7 which is dissolved gradually up to nano-scaled state exhibiting moderate SHG efficiency by analogy with nanostructured glasses because of space modulation of polarizability originated from nano-sized inhomogeneities enriched with Pb and Nb. Using of TeO2-based glasses permits to match reft active indexes of glass matrix and crystal, reduce glass melting temperature and fabricate transparent composites containing micron and sub-micron crystals with high second harmonic generation activity. [ABSTRACT FROM AUTHOR]

The microscopic theory of a transitional layer on the ideal surface of a semi-infinite absorbing or nonabsorbing isotropic dielectric is developed within the framework of classical optics when the polarization vector of the medium is a linear function of the electric field strength inside the medium. The concentration of atoms (molecules) of the medium and their polarizability are independent of coordinates and are constant inside the medium and close to its surface. The consideration is carried out within the framework of the concept of a discrete-continuous dielectric, in which the fields of dipoles of discretely distributed atoms (molecules) inside the Lorentz sphere surrounding the observation point are taken into account. The near-field effect is shown to result in a nonexponential behavior of the field nearby the surface. The thickness of the transitional layer can be found from experimental values of the reflected wave amplitude. [ABSTRACT FROM AUTHOR]

A boundary problem of linear classical optics is solved in which the behavior of the electromagnetic field near the surface of a dielectric medium is studied. It is shown that including the discrete structure of a medium into the analysis has the most substantial effect on the behavior of the electromagnetic field at distances smaller than 2a[sub 0], where a[sub 0] is the lattice constant. This fact makes it possible to obtain numerical estimates of the size of the region where the reflected and transmitted waves are formed. [ABSTRACT FROM AUTHOR]

The trigger for biomineralization of metazoans in the terminal Ediacaran, ca. 550 Ma, has been suggested to be the rise of oxygenation or an increase in seawater Ca concentration, but geochemical and fossil data have not been fully integrated to demonstrate cause and effect. Here we combine the record of macrofossils with early marine carbonate cement distribution within a relative depth framework for terminal Ediacaran to Cambrian successions on the eastern Siberian Platform, Russia, to interrogate the evolution of seawater chemistry and biotic response. Prior to ca. 545 Ma, the presence of early marine ferroan dolomite cement suggests dominantly ferruginous anoxic "aragonite-dolomite seas", with a very shallow oxic chemocline that supported mainly soft-bodied macrobiota. After ca. 545 Ma, marine cements changed to aragonite and/or high-Mg calcite, and this coincides with the appearance of widespread aragonite and high-Mg calcite skeletal metazoans, suggesting a profound change in seawater chemistry to "aragonite seas" with a deeper chemocline. By early Cambrian Stage 3, the first marine low-Mg calcite cements appear, coincident with the first low-Mg calcite metazoan skeletons, suggesting a further shift to "calcite seas". We suggest that this evolution of seawater chemistry was caused by enhanced continental denudation that increased the input of Ca into oceans so progressively lowering Mg/Ca, which, combined with more widespread oxic conditions, facilitated the rise of skeletal animals and in turn influenced the evolution of skeletal mineralogy. [ABSTRACT FROM AUTHOR]

Much uncertainty remains as to the temporal relationship between the Ediacaran and Cambrian biotas, yet this is critical to our understanding of the rise of metazoans. Here we present new high-resolution carbon isotope chemostratigraphy and biostratigraphy for a terminal Ediacaran to Cambrian succession on the eastern Siberian Platform, Russia, which shows the presence of a succession of diverse fossil assemblages before the start of the basal Cambrian negative carbon isotope excursion (BACE). Soft-bodied Ediacaran biota (Beltanelliformis) occur before the start of the late Ediacaran positive carbon isotope plateau (EPIP), a mixed Ediacaran and Cambrian skeletal biota (Cloudina, Anabarites, Cambrotubulus) appears within the EPIP, and diverse Cambrian-type small shelly fossils including Protohertzina and other protocondonts, halkieriids, chancelloriids, hyoliths, hyolithelminthes, and the burrowing trace fossil Diplocraterion appear at the beginning of the BACE. These integrated data show that taxa attributed to so-called Ediacaran and earliest Cambrian skeletal biotas in fact overlap without notable biotic turnover, and thus refute the presence of a large isotope excursion coincident with mass extinction of all Ediacaran biota. We propose a new biozone, the Cloudina-Namacalathus-Sinotubulites Assemblage Zone, to precede the known small shelly fossil (SSF) zones. These observations raise doubts as to whether there is any true separation between the Ediacaran and Cambrian skeletal biotas, and suggest that there is a deep root for the Cambrian explosion of metazoans. [ABSTRACT FROM AUTHOR]

Spatial coherence function (SCF) is a complex function of two spatial coordinates that, in general, carries more information than the bare intensity distribution. A fast and quantitatively accurate measurement of the SCF is extremely important for a range of applications in optical sensing and imaging. Here, we demonstrate an efficient two-step procedure for measuring the full-field complex coherence function. The measurement relies on an optimized design of a wavefront shearing interferometer capable of characterizing spatially inhomogeneous fields over an extended angular domain. The measurement precision is confirmed by the excellent agreement with a numerical estimation based on Fresnel calculations. We demonstrate that the sensitivity and the measurement range afforded by our instrument permits us to reliably describe the differences in the complex coherence functions that are due to subtle modifications in the shape, position, and orientation of radiation sources.

The traditional Monte Carlo technique of photon transport in random media describes only single point properties of light, such as its intensity. Here we demonstrate an approach that extends these capabilities to simulations involving properties of spatial coherence, a two-point characteristic of light. Numerical experiments illustrate the use of this Monte Carlo technique for describing the propagation of partially spatially coherent light through random multiply scattering media.