Condensed Matter Physics Commons^™

Quantum Coherence And Interference In Metallic Photonic Crystals And Hybrid Systems, Ali Hatef

Electronic Thesis and Dissertation Repository

In the first part of the thesis, we study the absorption coefficient of quantum dots doped in metallic photonic crystals under different circumferences. We study numerically the temporal evolution of the absorption coefficient profile where a probe field is applied to monitor the absorption process in two cases, when quantum dots are embedded lightly and densely. We also studied the effect of a changing plasma frequency on the absorption profile of quantum dots two possible field configurations. We show that the changes in plasma energy can take the system from the absorption region to the transparent and gain region.

As …

Spectroscopic Studies Of Melamine At High Pressure, Martin Donald Galley

UNLV Theses, Dissertations, Professional Papers, and Capstones

We have performed mid- and far- Infra Red (IR) absorption, Raman spectroscopy, and angular dispersive x-ray diffraction (XRD) studies on melamine under high pressure and room temperature. We have verified the presence of two prior reported phase transitions, the first between 1-2 GPa, and the second between 7-9 GPa. We have also found evidence of a third unreported phase transition between 14-16 GPa, during which, there was a sudden disappearance of all low energy peaks (^-1 ) in both the Raman and IR spectra. The far-IR peak movement experiences a discontinuity as the rate of peak movement suddenly changes. …

Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis

Roger A. Lewis

An unusual concept for a simple and inexpensive terahertz source is presented: unpeeling adhesive tape. The observed spectrum of this terahertz radiation exhibits a peak at 2 THz and a broader peak at 18 THz. The radiation is not polarized. The mechanism of terahertz radiation is tribocharging of the adhesive tape and subsequent discharge, possibly bremsstrahlung with absorption or energy density focusing during the dielectric breakdown of a gas. The accompanying optical emission is also a consequence of tribocharging.

Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis

Josip Horvat

An unusual concept for a simple and inexpensive terahertz source is presented: unpeeling adhesive tape. The observed spectrum of this terahertz radiation exhibits a peak at 2 THz and a broader peak at 18 THz. The radiation is not polarized. The mechanism of terahertz radiation is tribocharging of the adhesive tape and subsequent discharge, possibly bremsstrahlung with absorption or energy density focusing during the dielectric breakdown of a gas. The accompanying optical emission is also a consequence of tribocharging.

Excitation-Induced Ge Quantum Dot Growth On Si(100)-2x1 By Pulsed Laser Deposition, Ali Oguz Er

Physics Theses & Dissertations

Self-assembled Ge quantum dots (QD) are grown on Si(100)-(2×1) with laser excitation during growth processes by pulsed laser deposition (PLD). In situ reflection-high energy electron diffraction (RHEED) and post-deposition atomic force microscopy (AFM) are used to study the growth dynamics and morphology of the QDs. A Q-switched Nd:YAG laser (λ = 1064 nm, 40 ns pulse width, 5 J/cm² fluence, and 10 Hz repetition rate) were used to ablate germanium and irradiate the silicon substrate. Ge QD formation on Si(100)-(2×1) with different substrate temperatures and excitation laser energy densities was studied. The excitation laser reduces the epitaxial growth temperature …

Ultrafast High-Energy Electron Diffraction Study Of Photoexcited Bismuth Nanoclusters By Femtosecond Laser Pulses, Ahmed R. Esmail

Electrical & Computer Engineering Theses & Dissertations

The advancement in ultrafast electron crystallography (UEC) over the past few decades facilitated the study of structural dynamics in all phases of matter induced by femtosecond laser pulses. This technique became very powerful when the spatial resolution was combined with the temporal resolution, and succeeded in studying chemical reactions by ultrafast electron diffraction, bulk crystal phonons and melting by X-ray diffraction.

In this dissertation, I demonstrate the uniqueness of UEC and its potential in monitoring in real time the structural dynamics of bismuth (Bi) nanoclusters and islands induced by femtosecond laser pulses. Our approach to accomplish this task includes building …