Optical Polarization Effects of Rough and Structured Surfaces

Abstract

The reflection and scattering of light from surfaces is a topic that has been much discussed in the scientific literature. The application of optical methods for the characterization of surfaces and the understanding of natural phenomena is dependent on good models for the optical properties of surfaces and interfaces. In this work, we will examine three different aspects of the optical properties of surfaces and interfaces.

The measurement of polarization effects of surfaces is dependent on wellperforming Mueller matrix ellipsometers. While designing Mueller matrix ellipsometers for a single wavelength is trivial, the design of broad-band imaging ellipsometers is a much more challenging problem. We discuss the use of genetic algorithms to optimize such ellipsometers in a very general fashion, and apply them to ellipsometers based on various liquid crystal technologies. The results include an ellipsometer design which was patented, and which outperforms previous designs both in terms of spectral bandwidth and noise propagation.

Recent progress in the ability to manipulate matter on the nanoscale has led to great interest in the biological, chemical, and physical properties of nanoparticles and nano-sized structures. Depositing nanoparticles on top of a surface modifies the optical properties of both the particles as well as the substrate: any optical resonances that the particle(s) possess are modified by the substrate, and the reflectivity of the substrate is changed due to the presence of the particles. The electromagnetic interactions between nanoparticles and substrate are here investigated in the quasistatic regime, with discussion of both small clusters of nanoparticles as well as (infinite) periodic lattices of nanoparticles deposited on a substrate. The results include analysis of the interactions and resonances found in nanoparticle clusters deposited on a substrate.

When light is incident on surfaces possessing random roughness or structure, the light is scattered according to the statistical properties of the surface. While there has been significant progress on surface scattering from surfaces with one-dimensional surface profile functions, less attention has been devoted to numerical models of surfaces possessing two-dimensional surface profiles. The main reason for this is that the solution of these models requires a large amount of computational power, even by today’s standards. We attempt to shed some light on optical effects observed in scattering from two-dimensional rough surfaces, with some focus on polarization effects, which are absent in scattering from one-dimensional surfaces. The Mueller matrix for a rough surface is also calculated, and describes the full polarization effects of rough surface scattering.