Other Engineering Commons^™

Multifunctional Properties Of Gan Nws Applied To Nanometrology, Nanophotonics, And Scanning Probe Microscopy/Lithography, Mahmoud Behzadirad

Optical Science and Engineering ETDs

GaN nanowires are promising for optical and optoelectronic applications because of their waveguiding properties and large optical bandgap. Recent researches have shown superior mechanical properties of GaN nanowires which promises their use in new research areas e.g. nanometrology. In this work, we develop a scalable two-step top-down approach using interferometric lithography as well a bottom-up growth of NWs using MOCVD, to manufacture highly-ordered arrays of nanowires with atomic surface roughness and desired aspect-ratios to be used in nanophotonics and atomic precision metrology and lithography. Using this method, uniform nanowire arrays were achieved over large-areas (~1 mm²) with aspect-ratio …

Generation And Use Of Femtosecond, Gigawatt, Near Infrared Laser Pulses From An Amplified, Mode-Locked, Ti:Sapphire Laser, David Anthony Valdés

Optical Science and Engineering ETDs

This work modeled the early to middle successes achieved in the field of ultrafast, high peak power optics, beginning with the work of Nobel Prize winners Donna Strickland and Gérard Mourou in 1985. In our work, 100 fs light pulses of around 800 nm were generated by a Ti:Sapphire oscillator, then amplified to approximately 30 GW peak power using a chirped pulse amplification system that included regenerative and multi-pass amplifiers. As a verification of our pulses having high peak powers and ultrashort durations, they were then used to strike water, glass, and a Kerr Cell. Supercontinuum generation was observed as …

Sub-Nanometer Coupling Distance Control And Plasmon Enhanced Carrier Generation And Dynamics In Iii-V Semiconductor Heterostructures, Sharmin Haq

Optical Science and Engineering ETDs

Plasmonic modes in metal nanostructures enable light confinement at subwavelength scales. This field confinement is important for exploring the potential of nanotechnology in miniaturization of optics as well as for the advancement of optoelectronic devices, such as photodetectors, photovoltaics, and light-emitting diodes. Plasmon resonances are also ideal for developing ultrasensitive biosensors, and for enhancing surface photochemistry and photocatalysis. The increasing number of plasmon applications requires fundamental understanding of the plasmon coupled system which has not yet been completely understood. Controlling and engineering the plasmon response at the nanoscale will open still more applications in material science, communications, biochemistry and medicine. …

Transverse Anderson Localization In Optical Fibers: High-Quality Wave Transmission And Novel Lasing Applications, Behnam Abaie

Optical Science and Engineering ETDs

In this dissertation, transverse Anderson localization (TAL) of light mediated by disordered optical fibers is exploited for high-quality optical wave transmission and novel random lasing applications. En route, we first establish a powerful numerical platform for detailed investigation of TAL optical fibers (TALOF). Our approach is based on a modal perspective as opposed to beam propagation method (BPM) which was primarily used in the previous studies of TAL in disordered optical fibers. The versatile numerical tools developed in our simulations result in a potent methodology for simulation of TALOFs; the result is a fast and effective algorithm which can be …

Carrier Dynamics In High-Speed Iii-Nitride Light-Emitting Diodes For Visible-Light Communication, Arman Rashidi

Optical Science and Engineering ETDs

III-nitride light-emitting diodes (LEDs) are now ubiquitous in solid-state lighting (SSL) systems. Despite the significant advancement of III-nitride LEDs, the origins of fundamental challenges such as efficiency droop, thermal droop, and green gap are not completely understood. In addition, emerging applications such as micro-pixel LED displays and visible-light communication (VLC) require efficient LEDs capable of high-speed modulation. Studies of carrier dynamics are essential to better understand the fundamental efficiency challenges and enable the design of high-efficiency, high-speed LEDs. Among approaches to characterize the carrier dynamics in LEDs, electrically injected methods are preferred over optically pumped methods to capture the carrier …

Analytical Modeling And Characterization For Avalanche Photodiodes, Erum Jamil

Optical Science and Engineering ETDs

For applications requiring the detection of low light levels, avalanche photodiodes (APDs) are the preferred detector of choice. The reason for this is their internal gain, which improves the APDs sensitivity (up to 5 − 10 dB) when compared to PIN-based photodiodes. The internal gain for an APD comes from the process of impact ionization process; however, due to its stochastic nature, the multiplication gain comes at the expense of extra noise. This multiplication noise, called the excess noise, is a measure of the gain uncertainty. Despite significant progress made in the fabrication process for the APDs, the excess noise …

Anisotropy And Emission From Air With Laser Filaments, Mohammadamin Rasoulof

Optical Science and Engineering ETDs

Laser filaments are extremely interesting entities for their unique characteristics. The high intensity inside the laser filaments creates nonlinear effects that are useful in many areas of optics. The laser filamentation is an appealing tool in the stand-off spectroscopy for its ability to propagate over long distances while maintains its extreme intensity. However, depletion of energy hinders its propagation over any desired distance. In order to understand the effect of laser filaments on the transparent medium that they propagate through, one needs to investigate interaction of the laser filaments with the constituents of media. In this work we study the …

Spatio-Temporally Resolved Optical Laser-Induced Damage To Study Defect Limited Performance Of Optical Films, Yejia Xu

Optical Science and Engineering ETDs

Laser-induced damage (LID) limits the performance of optical films and surfaces. Despite intensive study for decades following the invention of laser, the study of LID remains timely and attractive, because for nanosecond laser pulses the LID process is controlled by randomly distributed defects of unknown origin.

Traditional damage tests yield little information about the defects present in optical films and surfaces. These methods record a "yes" or "no" damage result after each test and cannot distinguish the different defects present.

This dissertation focuses on the development of a new kind of laser-induced damage test that measures the actual fluence (intensity) …

Synchronous Generation And Coherent Control Of Extreme Wavelength Radiation And Ultrafast Spectroscopy, Aram Gragossian

Optical Science and Engineering ETDs

Recent progress in ultrafast laser science has made it possible to synthesize and control complex electromagnetic waveforms down to sub-femtosecond timescales. These tailored ultrashort laser pulses can generate coherent bursts of electromagnetic radiation in the extreme ultraviolet (XUV) and terahertz spectral regions with durations reaching the attosecond regime in the XUV region. This is accomplished by coherently controlling electronic motion in gas plasma targets. With these novel radiation sources, ultrafast time-resolved spectroscopy can be performed on a large variety of materials. Knowledge of the spectral phase of an ultrashort pulse is crucial for many applications. There are a variety of …

Scatterometry Of 50 Nm Half Pitch Features, Ruichao Zhu

Optical Science and Engineering ETDs

Metrology technologies are an essential adjunct to Integrated Circuit (I.C.) Semiconductor manufacturing. Scatterometry, an optical metrology, was chosen to measure 50 nm half pitch feature structures. A bread-board scatterometry system has been assembled to provide a non-contact, non-destructive, accurate and flexible measurement. A real-time, on-line scatterometry system has also been demonstrated and proven to provide a high throughput measurement.

Three different types of samples have been measured using the scatterometry setup. The wire-grid polarizer (WGP) sample has been made by Jet and Flash Nanoimprint Lithography with ~100 nm pitch and ~50 nm wide ~200 nm tall Al gratings on fused …

High Power Optically Pumped Semiconductor Lasers For Sodium Guidestar Applications, Shawn W. Hackett

Optical Science and Engineering ETDs

Optically pumped semiconductor lasers (OPSLs) are shown to provide a much more compact and less expensive source for illumination of the sodium layer of the mesosphere for use as a sodium laser guidestar via single and two photon excitation schemes. This represents a revolution in laser guidestar technology as the cost, size, and power requirements for a laser guidestar system are shown to have been decreased by an order of magnitude with guidestar performance shown to be similar to previous sources. Sodium laser guidestar sources for broadband simultaneous illumination of multiple lines are developed and simulated. Simulations are then compared …

Top-Down Cross-Section Controlled Iii-Nitride Nanowire Lasers, Changyi Li

Optical Science and Engineering ETDs

III-nitride nanowire lasers have drawn significant attention as potential compact coherent light sources for a wide range of applications such as on-chip communication, optical sensing, and solid-state lighting. For practical applications, control over the lasing properties is needed. For example, a single mode lasing is beneficial for reducing the pulse broadening and the signal errors during the optical communications. An annular-shaped beam could be potentially used for the atom trapping or the stimulated emission depletion spectroscopy. The polarization-sensitive on-chip optical components also require linear polarization. However, due to the compact size of nanowire lasers and the cross-sectional symmetry of the …

Linear Mode Cmos Compatible P-N Junction Avalanche Photodiode For Smart-Lighting Applications, Md. Mottaleb Hossain

Optical Science and Engineering ETDs

There is a need in emerging smart lighting concepts for a high-speed sensing capability to enable adaptive lighting (smart spaces) and visible light communication. One approach to address this need is to design and manufacture a novel complementary-metal—oxide—semiconductor (CMOS) compatible, cost-effective detector array and readout circuit (ROIC) that incorporates integrated waveguide detectors and avalanche photodiodes (APDs). This thesis focuses on the APD design and fabrication component of the sensing capability required by smart-lighting systems. Silicon CMOS compatible APDs are expected to provide high-speed and high-sensitivity sensors in terms of simplicity of design, low power consumption and cost-effectiveness for smart-lighting applications. …

Precise Characterization And Investigation Of Laser Cooling In Iii-V Compound Semiconductors, Chengao Wang

Optical Science and Engineering ETDs

The physics and engineering issues associated with laser cooling of III-V compound semiconductors, in particular GaAs double heterostructures (DHS), are theoretically and experimentally investigated. This research addresses the key concepts of external quantum efficiency (EQE) and parasitic background absorption in a semiconductor laser cooler. The external quantum efficiency describes how well recombination radiation is removed from the cooling device and is precisely measured by All-optical Scanning Laser Calorimetry (ASLC). Using this technique, a record external quantum efficiency of 99.5% has been obtained with a GaAs laser cooler held at 100 K. However, high background absorption has hindered the observation of …

Three-Dimensional Imaging Using A Novel Rotating Point Spread Function Imager, Rakesh Kumar

Optical Science and Engineering ETDs

The capability to achieve three-dimensional (3D) imaging in a single snapshot is a highly coveted goal for the imaging community. To be able to extend the depth-of-field while simultaneously encoding depth in the point spread function (PSF) itself allows an imaging solution which is less time consuming and less data intensive than the inefficient multiscan based conventional 3D imaging. Light-field cameras also achieve 3D imaging in a snapshot, but at the cost of greatly reduced resolution. Phase mask based depth encoding solutions have been proposed by other groups, but they all suffer from a relatively smaller depth-of-field. Recently there has …

Cramer-Rao Bound Analysis Of Multi-Frame Blind Deconvolution, Alim Haji

Optical Science and Engineering ETDs

This thesis explores how support constraints and multiple frames affect multi-frame blind deconvolution. Previous research in non-blind deconvolution, which seeks to estimate an object from a blurred and noisy image, characterized how the use of support constraints exploited spatial noise correlations to reduce noise in the estimate of the object. In multi-frame blind deconvolution, the blurring function is unknown and must be estimated along with the object. Applying a support constraint to both the object and the blurring functions, when using blind deconvolution, is one way to ensure a unique solution. The effects on the estimate of the object as …

Analysis Of A Laser Induced Plasma In High Pressure Sf6 Gas For High-Voltage, High-Current Switching, Waylon Clark

Optical Science and Engineering ETDs

The Laser Triggered Switch Program at Sandia National Laboratories is an intensive development study to understand and optimize the laser triggered gas switch (LTGS) for the Z-Refurbishment (ZR) project. The laser triggered gas switch is the final command-triggered switch in the machine, and reliability and performance of the switch is crucial. A modified LTGS trigger section with optical viewing windows perpendicular to the laser propagation is used to analyze a laser induced plasma spark in SF6 gas in order to quantify parameters such as spark length and plasma temperature. The laser spark is created through a focusing lens by the …