The objective of this Thesis is to design a scan lens for a long wave infrared laser marking system. The system is comprised of a laser source emitting a collimated beam coupled with a 14mm aperture dual axis galvanometer scanning system capable of scanning a range ± 11° (mechanical). Multiple scan lens options will be considered. Each scan lens will be optimized to maximize peak irradiance and operate at, or near, the diffraction limit over a 210x110 mm 'plus' shaped field. Unintended distortion evident in some lens designs and will be compensated for by developing equations that allowed the proprietary imaging algorithm to adjust the angle of the scanning mirror appropriately to achieve an undistorted image. The accuracy of the distortion correction will be within 1% of the shortest image dimension. Commercially available scan lenses are designed for generic scanning systems with no apriori knowledge of the imaging model and are typically available in arbitrary focal length increments. As a result, use of off the shelf scan lenses result in sub-optimal performance. This thesis presents background information on galvanometer based scanning systems followed by a review of classical scan lenses. The imaging application and systems constraints for the marking system are defined. The steps taken to design and optimize a conventional, aspheric, and F-Theta scan lens are described, and their performances are compared with respect to the design requirements. The Conventional scan lens coupled with a distortion correction equation was found to offer the best performance to cost ratio and was deemed the most appropriate lens for the marking system.

A Thulium Germanate thin disk laser prototype is developed and its potential applications are discussed. Unfortunately, the thin disk gain material for the CW prototype was unable to lase due to thermal limitations within the disk. However, a CW output power model and a physical pump chamber module have been developed, along with the supporting Zemax models and alignment procedures so other gain materials and future improvements can be tested.

The term biometrics is used to describe the process of analyzing biological and behavioral traits that are unique to an individual in order to confirm or determine his or her identity. Many biometric modalities are currently being researched and implemented including, fingerprints, hand and facial geometry, iris recognition, vein structure recognition, gait, voice recognition, etc... This project explores the possibility of using corneal topography measurements as a trait for biometric identification. Two new corneal topographers were developed for this study. The first was designed to function as an operator-free device that will allow a user to approach the device and have his or her corneal topography measured. Human subject topography data were collected with this device and compared to measurements made with the commercially available Keratron Piccolo topographer (Optikon, Rome, Italy). A third topographer that departs from the standard Placido disk technology allows for arbitrary pattern illumination through the use of LCD monitors. This topographer was built and tested to be used in future research studies. Topography data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing topography data and comparing one topographical measurement with a database for biometric identification. The data were analyzed to determine the biometric error rates associated with corneal topography measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.

Single-photon emission computed tomography (SPECT) is a modality widely used to detect myocardial ischemia and myocardial infarction. Objectively assessing and comparing different SPECT systems is important so that the best detectability of cardiac defects can be achieved. Whitaker, Clarkson, and Barrett's study on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than reconstruction data. Thus, this observer model assesses overall hardware performance independent by any reconstruction algorithm. In addition, we will show that the run time of image-quality studies is significantly reduced. Several systems derived from the GE CZT-based dedicated cardiac SPECT camera Discovery 530c design, which is officially named the Alcyone Technology: Discovery NM 530c, were assessed using the performance of the SLO for the task of detecting cardiac defects and estimating the properties of the defects. Clinically, hearts can be virtually segmented into three coronary artery territories: left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA). One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can correctly predict in which territory the defect exists. A good estimation of the defect extent from the images is also very helpful for determining the seriousness of the myocardial ischemia. In this dissertation, both locations and extent of defects were estimated by the SLO, and system performance was assessed using localization receiver operating characteristic (LROC) / estimation receiver operating characteristic (EROC) curves. Area under LROC curve (AULC) / area under EROC curve (AUEC) and true positive fraction (TPF) at specific false positive fraction (FPF) can be treated as the figures of merit (FOMs). As the results will show, a combination of the SLO and LROC / EROC curves can determine the configuration that has the most estimation/detection information and thus is a useful method for assessing cardiac SPECT systems.

Optically pumped semiconductor lasers (OPSLs) combine features including an engineerable emission wavelength, good beam quality, and scalable output power and are desirable for a wide variety of applications. Power scaling of OPSLs requires a combination of accurate epitaxial quantum design, accurate wafer growth and good thermal management. Here a fabrication process for OPSL devices was developed to ensure efficient OPSL device cooling and minimum surface scattering. A systematic thermal analysis was performed to optimize thermal management. Strategies for optimizing power extraction were developed; including increasing the gain/micro-cavity detuning that increases the threshold but also increases the slope efficiency and the roll-over temperature, recycling the excess pump via reflection from a metalized reflector at the back of a transparent DBR, anti-reflection coating at the pump wavelength while preserving the signal micro-cavity resonance. With optimized thermal management and the strategy of using large gain/micro-cavity detuning structure, a CW output power of 103 W from a single OPSL device was achieved. 42% optical-to-optical efficiency from the net pump power was obtained from the OPSL device with the double pass pump design and 39% optical-to-optical efficiency with respect to the total pump power was obtained with the new pump anti-reflection coating. For the fundamental mode operation, over 27 W of CW output power was achieved. To our knowledge, this is the highest 1 µm TEM₀₀ mode power reported to date for an OPSL. Finally, strategies for generating high peak power are also discussed. A maximum peak power of over 270 W was achieved using 750 ns pump pulses.

The lasers operating in the wavelength range of 900 - 1000 nm have caused intense attention because they are in great demands for: 1. Highpower blue and deep UV laser generation 2. High power single-mode pump laser source 3. Light detection and Lidar , etc. And now, there are actually many different types of lasers can generate laser in this wavelength range. For example, Nd and Yb doped fiber laser, Nd and Yb doped glass and crystal lasers, OPO and SHG laser, etc. Among all this options, we decided to study the Nd-doped fiber laser for their outstanding advantages: 1. As fiber laser, it possess all the advantages of any fiber lasers have, such as: high power scalability, excellent beam quality, high spectral and intensity stability, super compactness, robustness and reliability. 2. Comparing to other rare-earth-ion, the Nd^3+ ions have a more broad emission wavelength range from 900-950 nm. My goals for doing this thesis research are:1.Experimentally and theoretically investigate Nd-doped fiber lasers and amplifiers at 9xx nm. 2. Develop 9xx nm single frequency fiber lasers and amplifiers. 3.Obtain directions for developing high power single-frequency Nd-doped fiber laser sources at 9xx nm. To achieve these goals, 1. Nd-doped fiber lasers at 934 nm were investigated. 2. Core-pumped and cladding-pumped Nd-doped fiber amplifiers are also investigated. 3. The simulation of the Nd-doped fiber amplifiers have been done.

Optically pumped semiconductor vertical external cavity surface emitting lasers (VECSEL) were first demonstrated in the mid 1990's. Due to the unique design properties of extended cavity lasers VECSELs have been able to provide tunable, high-output powers while maintaining excellent beam quality. These features offer a wide range of possible applications in areas such as medicine, spectroscopy, defense, imaging, communications and entertainment. Nowadays, newly developed VECSELs, cover the spectral regions from red (600 nm) to around 5 µm. By taking the advantage of the open cavity design, the emission can be further expanded to UV or THz regions by the means of intracavity nonlinear frequency generation. The objective of this dissertation is to investigate and extend the capabilities of high-power VECSELs by utilizing novel nonlinear conversion techniques. Optically pumped VECSELs based on GaAs semiconductor heterostructures have been demonstrated to provide exceptionally high output powers covering the 900 to 1200 nm spectral region with diffraction limited beam quality. The free space cavity design allows for access to the high intracavity circulating powers where high efficiency nonlinear frequency conversions and wavelength tuning can be obtained. As an introduction, this dissertation consists of a brief history of the development of VECSELs as well as wafer design, chip fabrication and resonator cavity design for optimal frequency conversion. Specifically, the different types of laser cavities such as: linear cavity, V-shaped cavity and patented T-shaped cavity are described, since their optimization is crucial for transverse mode quality, stability, tunability and efficient frequency conversion. All types of nonlinear conversions such as second harmonic, sum frequency and difference frequency generation are discussed in extensive detail. The theoretical simulation and the development of the high-power, tunable blue and green VECSEL by the means of type I second harmonic generation in a V- cavity is presented. Tens of watts of output power for both blue and green wavelengths prove the viability for VECSELs to replace the other types of lasers currently used for applications in laser light shows, for Ti:Sapphire pumping, and for medical applications such as laser skin resurfacing. The novel, recently patented, two-chip T-cavity configuration allowing for spatial overlap of two, separate VECSEL cavities is described in detail. This type of setup is further used to demonstrate type II sum frequency generation to green with multi-watt output, and the full potential of the T-cavity is utilized by achieving type II difference frequency generation to the mid-IR spectral region. The tunable output around 5.4 µm with over 10 mW power is showcased. In the same manner the first attempts to generate THz radiation are discussed. Finally, a slightly modified T-cavity VECSEL is used to reach the UV spectral regions thanks to type I fourth harmonic generation. Over 100 mW at around 265 nm is obtained in a setup which utilizes no stabilization techniques. The dissertation demonstrates the flexibility of the VECSEL in achieving broad spectral coverage and thus its potential for a wide range of applications.

Thermal Barrier Coatings (TBCs), and plasma spray coatings in general, require critical control over the deposited thickness to achieve reliable coating performance. Currently, the plasma spray industry quantifies thickness by sampling the part before and after TBC deposition. Approximate thickness is thus inferred from previous runs. However, process variability can allow errors to propagate in this result that leads to wasted time and resources, and can ultimately lead to non-reliant coatings. To this end, an in situ optical fringe profilometer is developed that enables coating thickness measurements across a 2-dimensional surface. The initial profilometer concept is explored through requirements and trade studies, leading to a hardware and algorithm design family and prototype build to capture and compare real-world data to simulation and model predictions. This initial result shows a viable path-forward and the ability to achieve micrometer-scale depth resolution. Modifications and alterations to the in situ profilometer are then explored to improve the performance limits achievable. In specific, industrial spray coatings operate by dropping fine-grain media into a high pressure gas line aimed through a plasma torch to impart enough thermal and kinetic energy to stick to the part surface. This presents a challenging operational environment for an optical depth measurement sensor, working with a variable high-temperature blackbody stray light source; constant part rotation and plasma gun movement; and a non-isolated vibration environment. As such, the concept of the profilometer is further adapted specific to this end-purpose, by developing and reviewing both dual-fringe projection and plenoptic imaging. These techniques allow an improvement to both the system micro- and macroscopic depth retrieval limits, allowing a method to solve for an extended range of phase ambiguities and relax object focus requirements (respectively). The end result is a system concept and algorithm design that presents a feasible manner for automated in situ geometry and depth measurements in the plasma spray industry. The in situ fringe profilometer work described herein allows a flexible path to recover object depth information remotely, and is especially relevant for asymmetric and complex non-planar geometries, which are experiencing renewed interest with additive manufacturing processes and generally quite common to the thermal spray industry.

Ever since the first laser demonstration in 1960, applications for laser systems have increased to include diverse fields such as: national defense, biology and medicine, entertainment, imaging, and communications. In order to serve the growing demand, a wide range of laser types including solid-state, semiconductor, gas, and dye lasers have been developed. For most applications it is critical to have lasers with both high optical power and excellent beam quality. This has traditionally been difficult to simultaneously achieve in semiconductor lasers. In the mid 1990's, the advent of an optically pumped semiconductor vertical-external-cavity surface-emitting laser (VECSEL) led to the demonstration of high (multi-watt) output power with near diffraction limited (TEM00) beam quality. Since that time VECSELs covering large wavelength regions have been developed. It is the objective of this dissertation to investigate and explore novel cavity designs which can lead to increased functionality in high power, high brightness VECSELs. Optically pumped VECSELs have previously demonstrated their potential for high power, high brightness operation. In addition, the "open" cavity design of this type of laser makes intracavity nonlinear frequency conversion, linewidth narrowing, and spectral tuning very efficient. By altering the external cavity design it is possible to add additional functionality to this already flexible design. In this dissertation, the history, theory, design, and fabrication are first presented as VECSEL performance relies heavily on the design and fabrication of the chip. Basic cavities such as the linear cavity and v-shaped cavity will be discussed, including the role they play in wavelength tuning, transverse mode profile, and mode stability. The development of a VECSEL for use as a sodium guide star laser is presented including the theory and simulation of intracavity frequency generation in a modified v-cavity. The results show agreement with theory and the measurement of the sodium D1 and D2 lines are demonstrated. A discussion of gain coupled VECSELs in which a single pump area accommodates two laser cavities is demonstrated and a description of mode competition and the importance of spontaneous emission in determining the lasing condition is discussed. Finally the T-cavity configuration is presented. This configuration allows for the spatial overlap of two VECSEL cavities operating with orthogonal polarizations. Independent tuning of each cavity is presented as well as the quality of the beam overlap and demonstration of Type II intracavity sum frequency generation. Future applications to this configuration are discussed in the generation of high power, high brightness lasers operating from the UV to far-infrared and even terahertz regimes.

Interferometry with computer generated holograms (CGH) has evolved to be a standard technology for optical testing and metrology. By controlling the phase of the diffracted light, CGHs are capable of generating reference wavefronts of any desired shape, which allows using of interferometers for measuring complex aspheric surfaces. Fabrication errors in CGHs, however, cause phase errors in the diffracted wavefront, which directly affects the accuracy and validity of the interferometric measurements. Therefore, CGH fabrication errors must be either calibrated or budgeted. This dissertation is a continuation and expansion of the analysis and calibration of the wavefront errors caused by CGH in optical testing. I will focus on two types of error: encoding error and etching variation induced errors. In Topic one, the analysis of wavefront error introduced by encoding the CGH is discussed. The fabrication of CGH by e-beam or laser writing machine specifically requires using polygon segments to approximate the continuously smooth fringe pattern of an ideal CGH. Wavefront phase errors introduced in this process depend on the size of the polygon segments and the shape of the fringes. We propose a method for estimating the wavefront error and its spatial frequency, allowing optimization of the polygon sizes for required measurement accuracy. This method is validated with both computer simulation and direct measurements from an interferometer. In Topics two, we present a new device, the Diffractive Optics Calibrator (DOC), for measuring etching parameters, such as duty-cycle and etching depth, for CGH. The system scans the CGH with a collimated laser beam, and collects the far field diffraction pattern with a CCD array. The relative intensities of the various orders of diffraction are used to fit the phase shift from etching and the duty cycle of the binary pattern. The system is capable of measuring variations that cause 1 nm peak-to-valley (P-V) phase errors. The device will be used primarily for quality control of the CGHs. DOC is also capable of generating an induced phase error map for calibration. Such calibration is essential for measuring freeform aspheric surfaces with 1 nm root-mean-square (RMS) accuracy.