Light scattering

About: Light scattering is a research topic. Over the lifetime, 37721 publications have been published within this topic receiving 861581 citations.

Drude weight, plasmon dispersion, and ac conductivity in doped graphene sheets

Abstract: We demonstrate that the plasmon frequency and Drude weight of the electron liquid in a doped graphene sheet are strongly renormalized by electron-electron interactions even in the long-wavelength limit. This effect is not captured by the random-phase approximation (RPA), commonly used to describe electron fluids, and is due to coupling between the center-of-mass motion and the pseudospin degree of freedom of the graphene’s masslessDiracfermions.Bymakinguseofdiagrammaticperturbationtheorytofirstorderintheelectron-electron interaction, we show that this coupling enhances both the plasmon frequency and the Drude weight relative to the RPA value. We also show that interactions are responsible for a significant enhancement of the optical conductivity at frequencies just above the absorption threshold. Our predictions can be checked by far-infrared spectroscopy or inelastic light scattering.

Effects of aggregation on scattering and radiative properties of soot aerosols

Abstract: [1] The superposition T-matrix method is used to compute the scattering matrix elements and optical cross sections for a wide variety of fractal-like soot aggregates in random orientation at a visible wavelength 0.628 μm. The effects of the fractal dimension and prefactor, the monomer radius, the number of monomers in the aggregate, and the refractive index on light scattering and absorption by aggregated soot particles are analyzed. It is shown that the configuration of the monomers can have a substantial effect and that aggregation can result in a significant enhancement of extinction and scattering relative to those computed from the Lorenz–Mie theory, assuming that there are no electromagnetic interactions between the monomers. Thus one must take the effects of soot agglomeration and cluster morphology into account in radiative transfer modeling and remote sensing applications.

Structure of whispering-gallery modes in optical microdisks perturbed by nanoparticles

Abstract: It is a well-known fact that a single nanoparticle placed in the evanescent field of an optical microdisk leads to coherent backscattering of light between counterpropagating whispering-gallery modes. This backscattering lifts the spectral degeneracy giving rise to a doublet of standing-wave modes. Here, we show that the evanescent coupling of two or more nanoparticles leads in general to asymmetric backscattering (i.e., the strength of the scattering of light from the clockwise to the counterclockwise propagation direction is different than the other way around). Even if the strength of the backscattering is weak its asymmetry can have a dramatic impact on the mode structure. In the regime of overlapping resonances the modes do not have a standing-wave character. Instead nonorthogonal pairs of mainly copropagating modes are formed. In the extreme case the pair of optical modes coalesce at a so-called exceptional point. We derive an effective Hamiltonian within a two-mode approximation which reveals that this unexpected behavior is due to interference of the scattered waves which can be destructive or constructive depending on the propagation direction of the light.

Scattering and absorption of turbid materials determined from reflection measurements. 2: measuring method and calibration.

Abstract: A new experimental method has been developed to determine the scattering and absorption characteristics of a turbid material. Existing methods usually require transmission and reflection measurements carried out on a thin slab of the material under study; this method is based on reflection measurements carried out on bulk material. This will be of great advantage in many applications. This paper describes the measuring system and indicates the area of application of the method. Calibration measurements have been carried out to substantiate the approach.

Wave‐length dependencies of light scattering in normal and cold swollen rabbit corneas and their structural implications

Abstract: 1. The studies described herein involve the use of light scattering measurements to characterize the ultrastructural arrangement of the constituent collagen fibrils in rabbit corneal stromas. 2. Theoretical light scattering techniques for calculating the scattering to be expected from the structures revealed by electron micrographs are discussed, and comparison with the experimental light scattering tests the validity of these structures. 3. The wave-length dependence of light transmission and of angular light scattering from normal corneas is in agreement with the short range ordering of collagen fibrils depicted in electron micrographs. 4. The transmission measurements on oedematous rabbit corneas indicate that transmission decreases linearly with the ratio of thickness to normal thickness. 5. The wave-length dependence of transmission through cold swollen corneas indicates that the increased scattering is caused by large inhomogeneities in the ultrastructure. Electron micrographs do, indeed, reveal the presence of such inhomogeneities in the form of large regions completely devoid of fibrils.