Physics Commons^™

Ultrafast Laser-Induced Damage And The Influence Of Spectral Effects, Jeremy R. Gulley

Faculty and Research Publications

Numerous studies have investigated the prerequisite role of photoionization in ultrafast laser-induced damage (LID) of bulk dielectrics. This study examines the role of spectral width and instantaneous laser frequency in LID using a frequency dependent multiphoton ionization (MPI) model and numerical simulation of initially 800 nm laser pulses propagating through fused silica. Assuming a band gap of 9 eV, MPI by an 800 nm field is a six-photon process, but when the instantaneous wavelength is greater than 827 nm an additional photon is required for photoionization, reducing the probability of the event by many orders of magnitude. Simulation results suggest …

"Tuning Hole Mobility In Inp Nanowires", Mariama Rebello Sousa Dias, A. Picinin, V. Lopez-Richard, S. E. Ulloa, L. K. Castelano, J. P. Rino, G. E. Marques

Physics Faculty Publications

Transport properties of holes in InP nanowires (NWs) were calculated considering electron-phonon interaction via deformation potentials, the effect of temperature, and strain fields. Using molecular dynamics, we simulate NW structures, the longitudinal optical phonon (LO-phonon) energy renormalization, and lifetime. The valence band ground state changes between light- and heavy-hole character, as the strain fields and the NW size vary. Drastic changes in the mobility arise with the onset of resonance between the LO-phonons and the separation between valence subbands.

Phase Control In Atomic Coherence, Utsab Khadka

Graduate Theses and Dissertations

In this thesis, atomic coherence is used to enhance nonlinear optical processes in multi-level atoms. The multi-photon transitions are driven resonantly, and at the same time without absorptive losses, by using electromagnetically induced transparency (EIT), thereby allowing the study of χ⁽³⁾ and χ⁽⁵⁾ nonlinearities using weak driving fields. The coherently modified probe beam(s) and the atom-radiated signal fields arising from four- and six- wave- mixing (FWM and SWM) processes are measured in the spectral, temporal and spatial domains.

In a three-level ladder-type atomic system, multiple peaks having spectral asymmetries are observed in the EIT window as well as …

Third Order Nonlinearity Of Organic Molecules, Honghua Hu

Electronic Theses and Dissertations

The main goal of this dissertation is to investigate the third-order nonlinearity of organic molecules. This topic contains two aspects: two-photon absorption (2PA) and nonlinear refraction (NLR), which are associated with the imaginary and real part of the third-order nonlinearity (χ (3)) of the material, respectively. With the optical properties tailored through meticulous molecular structure engineering, organic molecules are promising candidates to exhibit large third-order nonlinearities. Both linear (absorption, fluorescence, fluorescence excitation anisotropy) and nonlinear (Z-scan, two-photon fluorescence, pump-probe) techniques are described and utilized to fully characterize the spectroscopic properties of organic molecules in solution or solid-state form. These properties …

Quantum-Dot Mode-Locked Lasers With Optical Injection, Tatiana Habruseva

Theses

In this thesis novel stabilised ultra-fast pulse sources for a range of practical applications have been developed.

Semiconductor mode-locked lasers have much promise as sources of short, low- jitter, high repetition rate pulses. Development of stabilised semiconductor sources is in a great demand for applications, such as optical telecommunications, frequency metrology, optical sampling and clock recovery. Arbitrary waveform generation, wavelength-division and orthogonal-frequency-division multiplexing techniques need wide stable frequency combs with low phase noise. A low level of pulse-to-pulse timing fluctuations is essential for clock recovery, optical sampling and optical time- division multiplexing. Therefore, this work dealing with the development of …