Multiple light scattering from metal and dielectric rough surfaces

A numerical study is done on light scattering from one-dimensional random rough surfaces supporting both dielectrics and metals. The influence of the corrugation on the Brewster angle as well as on the angular distribution of transmitted intensity into the dielectric is investigated. The authors also obtain enhanced backscattering in the light reflected from metallic surfaces. Finally they discuss the influence of roughness on the drop of reflectance due to polariton absorption.     

Multiple light scattering from metal and dielectric rough surfaces

Abstract

A numerical study is done on light scattering from one-dimensional random rough surfaces supporting both dielectrics and metals. The influence of the corrugation on the Brewster angle as well as on the angular distribution of transmitted intensity into the dielectric is investigated. The authors also obtain enhanced backscattering in the light reflected from metallic surfaces. Finally they discuss the influence of roughness on the drop of reflectance due to polariton absorption.     

Strong-field above-threshold photoemission from sharp metal tips

We present energy-resolved measurements of electron emission from sharp metal tips driven with low energy pulses from a few-cycle laser oscillator. We observe above-threshold photoemission with a photon order of up to 9. At a laser intensity of ～ 2 × 10(11) W/cm2 the suppression of the lowest order peak occurs, indicating the onset of strong-field effects. We also observe peak shifting linearly with intensity, with a slope of around -1.0 eV/(10(12) W/cm2). We attribute the magnitude of the laser field effects to field enhancement taking place at the tip's surface.     

Quantum size effects in the elastic scattering of light from small metal particles

A quantum mechanical calculation of the differential elastic scattering cross-section of light from a metal microparticle is presented. The scattering intensity is found to exhibit oscillations as a function of the frequency due to the discreteness of the electron energy levels. The magnitudes of the oscillations have a sensitive dependence on the size of the electron mean free path relative to the diameter of the particle.     

Surface monitoring based on light scattering by metal nanosensors

Light scattering from objects in the proximity of surfaces is of fundamental importance in a variety of surface- and field-enhanced optical sensing, spectroscopy and microscopy applications. Here, we present surface monitoring techniques based on the spectral analysis of the scattered light by metal nanoparticles which act as sensors (nanosensors) of sample substrates interacting with them. We will focus on the detection of surface inhomogeneities by studying the modifications undergone by the local fields produced in the surrounding of the nanosensor, giving rise to spectral changes in its Plasmon Resonances. We will also describe an alternative technique where the sample information is obtained from the changes induced in the linear polarization degree of the far field scattered by the tip and due to the interaction with the sample.     

Plasmonic couplers with metal nonlinearities

Usually nonlinear response of metals is neglected in the study of plasmonic waveguiding structures. Recent prediction of strong third-order optical response of metals due to ponderomotive forces opens up novel possibilities for utilizing this effect in the design of active plasmonic devices. We discuss the possibility of implementation of nonlinear response of metals in the design of plasmonic coupler. We analyze the structure and dispersions of linear and nonlinear guided plasmonic modes of two coupled thin metallic films and predict bifurcations of symmetry breaking.     

Perturbation theory results for the diffuse scattering of light from two-dimensional randomly rough metal surfaces

Abstract

Using the unitarity and reciprocity preserving formulation of Brown et al a perturbation treatment, correct to fourth order in the surface profile function, is given for the scattering of electromagnetic waves from a weakly rough, two-dimensional, random metal surface. In this formulation the boundary conditions on the electromagnetic fields are satisfied using the extinction theorem in conjunction with the Rayleigh hypothesis and the vector equivalent of the Kirchhoff integral. The theory is applied to, and results are presented for, several different types of rough surfaces which are characterized by power spectra that are extensions to two-dimensional random surfaces of the power spectrum of some one-dimensional random surfaces recently fabricated by West and O'Donnell. These surfaces, which can be realized experimentally, favor coherent, interferent, multiple scattering of electromagnetic waves via surface plasmon polaritons in intermediate states, and clearly exhibit enhanced backscattering caused by the surface plasmon polariton mechanism. Theoretical results are presented for silver surfaces at optical wavelengths.     

Perturbation theory results for the diffuse scattering of light from two-dimensional randomly rough metal surfaces

Using the unitarity and reciprocity preserving formulation of Brown et al a perturbation treatment, correct to fourth order in the surface profile function, is given for the scattering of electromagnetic waves from a weakly rough, two-dimensional, random metal surface. In this formulation the boundary conditions on the electromagnetic fields are satisfied using the extinction theorem in conjunction with the Rayleigh hypothesis and the vector equivalent of the Kirchhoff integral. The theory is applied to, and results are presented for, several different types of rough surfaces which are characterized by power spectra that are extensions to two-dimensional random surfaces of the power spectrum of some one-dimensional random surfaces recently fabricated by West and O'Donnell. These surfaces, which can be realized experimentally, favor coherent, interferent, multiple scattering of electromagnetic waves via surface plasmon polaritons in intermediate states, and clearly exhibit enhanced backscattering caused by the surface plasmon polariton mechanism. Theoretical results are presented for silver surfaces at optical wavelengths.     

Depolarized light scattering from simple fluids

It is shown that even in single scattering approximation, the light scattered by a simple fluid exhibits a depolarized component which arises from including additional terms in the current density. A new way of measuring the shear viscosity of a fluid is proposed.     

Depolarised light scattering from liquid pyridine

The depolarised light scattering spectra of liquid pyridine allow us to confirm the attribution of rotational diffusion constants proposed by Kintzinger and Lehn. We also observe the presence of collective modes.     

Depolarized light scattering from swollen-filled rubber

The H_v small-angle light-scattering patterns from cross-linked swollen rubbers containing glass bead filler particles are shown to arise from the birefringence patterns associated with the inhomogeneous swelling in the vicinity of the particles. Theoretically calculated patterns are obtained by using the stress field calculated by Sternstein and are found to agree with the experimental results.     

Electron light scattering from doped silicon

The light scattering from homogeneous intervalley fluctuations of free carriers density in n-Si is calculated for any degree of the electron gas degeneration. Effects of the external stress on the scattering spectrum are considered. Results allow to explain the basic qualitative results of the experiment [7].     

Plasmonic slow light waveguide and cavity

In this work, we present a detailed analysis of optical properties of metal–insulator and metal–insulator–metal (MIM) structure-based surface-plasmon waveguides and cavities. It is shown from the dispersion relation, the field distribution, the quality factor Q, and the transmission spectrum that the MIM structure can be designed as a high-Q cavity, supporting slow light with tolerable pulse distortion and lower propagation loss in the axial direction.     

White light scattering from non-Gaussian rough surfaces

Optics and Spectroscopy - A method is proposed for calculating the spectral correlation function of light intensity scattered from non-Gaussian rough surfaces. The correlation function of a...     

Surface roughness measurements from coherent light scattering

Results are presented of surface roughness measurements obtained by applying Beckmann's theory on the scattering of electromagnetic waves from rough surfaces to the scattering of laser light from ground glass surfaces. Measurements of the variance of surface height obtained in several scattering geometries and also from stylus measurements are presented and shown to agree closely for each surface. Also results are presented which show that the usual assumption of a Gaussian form for the autocorrelation function of surface height does not apply to the surfaces being studied here.