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The scattering phase functions of micrometer-sized glycerol droplets containing spherical latex inclusions undergo random fluctuations with time. We measure scattering intensities in the near-forward and near-backward scattering directions and find them to have strong positive correlations during some time periods and strong negative correlations during other time periods. The characteristic time constants of these correlations are of the order of seconds. We calculate scattering correlations from two types of scattering system. Correlations from a two-sphere system generally are positive, whereas correlations from a sphere containing a single spherical inclusion may be both positive and negative. Calculations of correlations from our experimental data are consistent with diffusion of inclusions within the host droplet, rather than interference effects between the inclusions.

We show that the far fields generated by a source inside or near a microparticle can be obtained readily by using the reciprocity theorem along with the internal or near fields generated by plane-wave illumination. This method is useful for solving problems for which the scattered fields generated with plane-wave illumination have already been obtained. We illustrate the method for the case of a homogeneous sphere and then apply it to the problem of emission from a dipole inside a sphere that is near a plane interface.

A prominent characteristic of the light scattered from a microparticle containing inclusions is a fluctuation in the intensity that is due to the changing positions of the inclusions with respect to each other and the host droplet. We calculate the magnitude of these fluctuations for a host sphere containing a single eccentrically located spherical inclusion and experimentally measure the fluctuation amplitudes for host spheres containing multiple inclusions. We find that, for sufficiently small single inclusions, the amplitude of the scattering fluctuations increases approximately linearly with the area of the inclusion. For multiple inclusions, the fluctuation amplitude increases with concentration with an approximate power-law dependence.

For some applications, it has been assumed that scattering from an object placed near a highly reflecting substrate such as aluminum can be approximated by the scattering from that object placed near a perfectly conducting substrate. We examine this approximation by comparing the calculated scattering from dielectric spheres resting on plane substrates that are perfectly conducting and composed of aluminum. Examination of the Mueller polarization matrix elements shows appreciable differences between these two scattering systems. The differences, however, become small at scattering angles where the intensities are relatively large.

We derive a theory to calculate light scattering from a cylinder on or near a plane interface. There are no restrictions on the values of the refractive indices of the system constituents. We use the approximation that the interference component of the electromagnetic fields strikes the plane interface at normal incidence. The exact solution is asymptotically approached when either the cylinder–interface separation is large compared with the cylinder radius or the difference between the refractive indices separated by the plane interface becomes large or approaches zero. We compare numerical results with experimental Mueller matrix elements measured from a quartz fiber on an aluminum substrate. We find that numerical results calculated with this approximation are a significant improvement over those calculated assuming the interface to be perfectly conducting and those that do not include the interaction fields.

We found that the resonance positions for a weakly absorbing sphere are much different from those of a nonabsorbing sphere. The shifts of resonance positions for Qext, Qsca, and Qabs from their original resonance positions for a real refractive index are different, and the formulas to describe these different kinds of shift are given. Calculations of 12 resonance cases show that our results are quite close to those given by exact Lorenz–Mie theory. We also derive the line shapes of the different resonances and calculate values for the resonance maxima and half-width as a function of absorption.

We study the optical properties of anthropogenic sulfate aerosols containing black carbon using a recently developed exact solution of the scattering problem for a spherical particle (sulfate aerosol) containing an eccentrically located spherical inclusion (black carbon). We present the expression for the change of planetary albedo due to addition of an absorbing, but optically thin aerosol layer and estimate the effect of the black carbon within the sulfate aerosol layer on the aerosol direct radiative forcing. The black carbon within the sulfate aerosol reduces the expected sulfate direct cooling effect by about 0.034 W/m 2 for each 1% of the black carbon to sulfate mass mixing ratio. Thus the presence of black carbon within sulfate in the background aerosol does not significantly change the previous estimates of the global aerosol direct cooling effect. However, in regions where the black carbon in sulfate concentrations are of the order of 5% or more, the local and regional effects are significant. Briegleb, 1993) suggest that the effect of anthropogenic sulfates and aerosols produced by tropical biomass burning may be sufficient to counteract any possible warming trend due to an increase of atmospheric greenhouse gases generated since the beginning of the industrial revolution. The direct cooling effect of aerosols will be reduced by the presence of black carbon. Black carbon (soot) within aerosol particles increases the absorption of solar radiation and de- creases the reflection (albedo). In this paper we (1) calculate the optical properties of sul- fate aerosol containing black carbon using a recently devel- oped exact solution of the scattering problem by a spherical particle (sulfate aerosol) containing an eccentrically located spherical inclusion (black carbon), (2) present the expression for the change of planetary albedo due to the addition of an absorbing aerosol layer, and (3) estimate the effect of the black carbon within a sulfate aerosol layer on the aerosol direct radiative forcing.

The light scattered by a sphere behind a plane surface is solved with an extension of Mie theory. I solve the boundary conditions at the sphere and at the surface simultaneously and develop the scattering amplitude and Mueller scattering matrices. This approach involves the multiplication of the fields in the half-space region not including the sphere by an appropriate Fresnel reflection coefficient and the projection of these fields onto the half-space region including the sphere. The scattered fields from the sphere, reflecting off the surface and interacting with the sphere, are assumed to be incident upon the surface at near-normal incidence. The exact scatter approaches this limit when (1) the sphere is at a large distance from the surface, (2) the sphere radius is small compared with the incident wavelength, or (3) the difference between the refractive indices of the two half-space regions is either small or great.

We examine four theories that predict the scattered radiation from a system composed of a small sphere and a plane and show that in the far field the scattering amplitude components predicted by these theories are essentially the same. We express the scattering intensities in Mueller matrix representation and examine the far-field Mueller matrix as a function of various parameters.

A facet model is used to predict the polarization states of light scattered from rough surfaces. The states are compared with experimentally determined elements from various types of rough substrates. The experimental data are found to be quite similar to what is predicted by the model.

The light-scattering Mueller matrix is experimentally determined for a 0.26-μm-radius quartz fiber mounted on an aluminum surface at five different incident angles. The results are compared with those for the experimental scattering elements of the lone fiber and the lone surface and with theoretical results derived from a simple fiber–surface model. The experimental matrix elements of the fiber–surface system do not resemble the matrix elements from any of these other systems.

A ray-tracing model was used to derive the light scattering Mueller matrix element curves for a dipole near a perfect surface as a function of incident angle, scattering angle, and surface refractive index. This system represents a fundamental system composed of a perfect plane surface and a perfect (Rayleigh) scatterer.

The light-scattering problem of a sphere on or near a plane surface is solved by using an extension of the Mie theory. The approach taken is to solve the boundary conditions at the sphere and at the surface simultaneously and to develop the scattering amplitude and Mueller scattering matrices. This is performed by projecting the fields in the half-space region not including the sphere multiplied by an appropriate Fresnel reflection coefficient onto the half-space region including the sphere. An assumption is that the scattered fields from the sphere, reflecting off the surface and interacting with the sphere, are incident upon the surface at near-normal incidence. The exact solution is asymptotically approached when either the sphere is a large distance from the surface or the refractive index of the surface approaches infinity.

We derive an analytical parameterization of the amplitude and Mueller scattering matrices of a system composed of a small number of electric dipoles. The appeal of this derivation is that it provides a wide range of light-scattering polarization states with a minimal number of parameters. Such a tool can be used to interpret observations in terms of physical parameters. We aim to utilize these results in multiple-scattering studies, such as the interpretation of polarimetric and photometric phase effects of asteroids and other atmosphereless solar-system objects.

Light scattering resonances in small particles are analyzed either exactly or by approximate expressions for the most important Mie coefficients. Materials with different optical properties, incluiding Double Negative (as corresponding to LHM), are considered.

We present a methodology to characterize nanometer-size particles on or near a surface via surface-wave scattering. With a series of simulations, we show that the size of nano-particles on a metallic surface can be determined unambiguously from the angular profile of the elliptical polarization of scattered waves expressed as normalized scattering Mueller matrix elements M ij . This characterization modality is based on the interaction of particles on a surface with the evanescent waves. The particle–surface interactions become less pronounced with separation distance, and the scattering of evanescent waves by nano-particles does not show any significant size dependence. The results suggest that it is possible to monitor the self-assembly process of metallic particles on metallic surfaces in real time, which is crucial for on-line control in bottom-up nano-manufacturing processes.

Atmosphereless solar-system objects exhibit two ubiquitous light-scattering phenomena at small solar phase angles (sun.object.observer angle α): first, the opposition effect in the intensity of scattered sunlight (e.g., [1]); and, second, the negative degree of linear polarization (I ┴ − I ║)/(I ┴ + I ║). Here I ║ denotes the intensity component parallel to the scattering plane defined by the Sun, the object, and the observer and I ┴ denotes the component perpendicular to that plane [2].

There are two widely accepted restrictions on the application of the discrete dipole approximation (DDA) in the study of light scattering by particles comparable to the wavelength: (1) when considering dielectric particles, the size of the cells must satisfy the condition kd|m| < 0.5, where k is the wave-number, d is the size of the cells, and m is the complex refractive index of the constituent material and (2) when considering conductive particles, the size of the cells must be small enough to reproduce sufficiently the evolution of the electromagnetic field in the skin layer. We examine both restrictions when the DDA is applied to irregularly shaped particles and show that its restrictions are not as strong as is widely accepted. For instance, when studying irregularly shaped particles averaged over orientations, even at kd|m| = 1, the DDA provides highly accurate numerical results. Moreover, we show that the impact of using large constituent cells is similar to that produced by surface roughness; therefore, the replacement of the target particle by an array of large constituent cells has the same effect, qualitatively, as incorporating additional small-scale surface roughness on the particle. Such a modification of the target particle can be desirable in many practical applications of DDA when irregularly shaped particles are considered. When applying DDA to conductive, nonspherical particles, the insufficient description of the electromagnetic field in the skin layer does not lead to a violation of the Maxwell equations, although it has a visible but nonmajor influence on the light-scattering properties of the target.