Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Elford Published Materials Science The work presented in this thesis is concerned with the propagation of acoustic waves through phononic crystal systems and their ability to attenuate sound in the low frequency regime. The plane wave expansion method and finite element method are utilised to investigate the properties of conventional phononic crystal systems. The acoustic band structure and transmission measurements of such systems are computed and verified experimentally.
Two ECE Graduates Win Sigma Xi Best Ph.D. Thesis Awards
Discoveries in Phononic Crystals and Acoustic Metamaterials
Petrus, J. A square lattice of shallow, noncylindrical holes in GaAs is shown to act as a phononic crystal PnC reflector. The holes are produced by wet-etching a GaAs substrate using a citric acid:H2O2 etching procedure and a photolithographed array pattern. Although nonuniform and asymmetric etch rates limit the depth and shape of the phononic crystal holes, the matrix acts as a PnC, as demonstrated by insertion loss measurements together with interferometric imaging of surface acoustic waves propagating on the GaAs surface. The measured vertical displacement induced by surface phonons compares favorably with finite-difference time-domain simulations of a PnC with rounded-square holes.
US9291297B2 - Multi-layer phononic crystal thermal insulators - Google Patents
A photonic crystal is a periodic optical nanostructure that affects the motion of photons in much the same way that ionic lattices affect electrons in solids. Photonic crystals occur in nature in the form of structural coloration and animal reflectors , and, in different forms, promise to be useful in a range of applications. In the English physicist Lord Rayleigh experimented with periodic multi-layer dielectric stacks, showing they had a photonic band-gap in one dimension. Research interest grew with work in by Eli Yablonovitch and Sajeev John on periodic optical structures with more than one dimension—now called photonic crystals.
When: Wednesday, February 3, pm - pm Speaker: Elizabeth Michiko Ashley, Nealey Group Description: Title: Using Block-Copolymer Nanolithography to Fabricate Ultrafine Phononic Crystals Abstract: In recent years, phononic crystals have emerged as a possible route for engineering the thermal properties of semiconductor materials like silicon independently of their electronic properties. Heat carriers, or thermal phonons, in Si are very difficult to manipulate due to their wide range of frequencies and nanoscale size. Nanostructures are requires to most effectively manipulate thermal phonos, but are extremely difficult to fabricate due to resolution limitations of modern lithography equipment. In this talk, I will present several different block-copolymer nanolithography-based approaches for fabricating sub-resolution limit hexagonal arrays of holes at a pitch of