Theory and Experiments of Scattering From Microscale Random Rough and Deterministic Surfaces

Surface scattering has received considerable attention in the last few decades and is of interest in various engineering disciplines including thermal system design, optical remote sensing and photorealistic image generation. A combined experimental and theoretical investigation has been conducted for surfaces which have surface length scales on the order of the incident wavelength. A Fourier Transform Infrared Spectrometer (FTIR) is used for experimental measurements from two-dimensional rough random surfaces, and one- and two-dimensional deterministic samples. The two-dimensional deterministic surfaces are fabricated in a manner similar to the manufacturing of Micro-Electro-Mechanical Systems (MEMS). Rigorous electromagnetic theory analysis is used to demonstrate the influence of the surface materials, incident wavelength, incident angles and surface geometric parameters on the reflection distribution. A geometric optics approximation to the rigorous electromagnetic theory is developed for random rough surfaces. The approximate results agree well with the FTIR experimental findings, indicating that the geometric optics approximation provides a relatively simple approach to quantify surface scattering for its validity domain. Furthermore, this approximation can predict specular, diffuse and retro-reflection characteristics. A statistical method is developed based on the geometric optics approximation. Although this model has a smaller domain of application compared to the geometric optics approximation, it provides accurate trend predictions and is computationally inexpensive. For one-dimensional deterministic samples, rigorous electromagnetic theory calculations are necessary, and the experimental findings are in good agreement with the theoretical predictions. The samples exhibit specular reflection for longer incident wavelengths, and modal reflection is observed for short incident wavelengths. For two-dimensional surfaces, the experimental results indicate that the one-dimensional rigorous electromagnetic theory can predict modal reflection only in specific and limited cases.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Tang, Kakuen

Contributors dc:contributor

• Buckius, Richard O.

• Engineering, Mechanical

Language dc:language

eng

Identifier

(MiAaPQ)AAI9912395

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/83979