Keywords

Scattering, speckle, polarimetry, spectroscopy

Abstract

The interaction of optical waves with material systems often results in complex, seemingly random fields. Because the fluctuations of such fields are typically difficult to analyze, they are regarded as noise to be suppressed. Nevertheless, in many cases the fluctuations of the field result from a linear and deterministic, albeit complicated, interaction between the optical field and the scattering system. As a result, linear systems theory (LST) can be used to frame the scattering problem and highlight situations in which useful information can be extracted from the fluctuations of the scattered field. Three fundamental problems can be posed in LST regardless of the nature of the system: one direct and two inverse problems. The direct problem attempts to predict the response of a known system to a known input. The problem may be simple enough to admit analytical solutions as in the case of homogeneous materials, phase and amplitude screens, and weakly scattering materials; or the problem may require the use of numerical techniques. This dissertation will focus on the two inverse problems, namely the determination of either the excitation field or the scattering system. Traditionally, the excitation determination problem has relied on designing optical systems that respond to the property of interest in a simple, easily quantified way. For example, gratings can be used to map wavelength onto direction of propagation while waveplates and polarizers can map polarization properties onto intensity. The primary difficulty with directly applying the concepts of LST to scattering systems iv is that, while the outputs are still combinations of the inputs, they are not ``simple'' combinations such as Fourier transforms or spatially dispersed spectral components of the input spectrum. Instead, the scattered field can be thought of as a massive sampling and mixing of the excitation field. This dissertation will show that such complicated sampling functions can be characterized and that the corresponding scattering medium can then be used as an optical device such as a lens, polarimeter, or spectrometer. The second inverse problem, system determination, is often more difficult because the problem itself may be ill-posed. For scattering systems that are dominated by low-order scattering, the statistical properties of the scattered light may serve as a fingerprint for material discrimination; however, in many situations, the statistical properties of the output do not depend on the material properties. Rather than analyzing the scattered field from one realization of the random interaction, several measurement techniques have been developed that attempt to extract information about the material system from modifications of the scattered field in response to changes in either the excitation or the intrinsic dynamics of the medium itself. One such technique is dynamic light scattering. This dissertation includes an extension to this method that allows for a polarimetric measurement of the scattered light using a reference beam with controllable polarization. Another system determination problem relates to imaging the reflectivity of a target that is being randomly illuminated. It will be demonstrated that an approach based on the correlation between the integrated scattered intensity and the corresponding illumination intensity distribution can prove superior to standard imaging microscopy

Notes

If this is your thesis or dissertation, and want to learn how to access it or for more information about readership statistics, contact us at STARS@ucf.edu

Graduation Date

2012

Semester

Fall

Advisor

Dogariu, Aristide

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

Optics and Photonics

Degree Program

Optics

Format

application/pdf

Identifier

CFE0004786

URL

http://purl.fcla.edu/fcla/etd/CFE0004786

Language

English

Release Date

June 2016

Length of Campus-only Access

3 years

Access Status

Doctoral Dissertation (Open Access)

Subjects

Dissertations, Academic -- Optics and Photonics, Optics and Photonics -- Dissertations, Academic

Download

Share

COinS