The fluorescence-emission spectra of normal arterial tissues and atherosclerotic plaques are distinct. The fluorescence spectra of arterial tissues are also dependent on the illumination wavelength. Which illumination wavelengths are best for identifying arterial tissues? To answer this question, a system for measuring fluorescence spectra at different illumination wavelengths was constructed and the fluorescence spectra of in-vitro aorta specimens were acquired with several illumination wavelengths between 270 nm and 500 nm. The Mahalanobis distance, a statistical measure of separability between two class density-distributions, was used to compare spectral features of normal vessel and atherosclerotic plaques at each of the illumination wavelengths. The Mahalanobis distance results indicated that the separability was largest for illumination wavelengths in the 314 nm to 334 nm range. In addition, the atherosclerotic plaque class was further subdivided into three diseased subclasses--fibrous plaques, complicated plaques and hard calcified plaques. The largest Mahalanobis distance between normal vessel and soft plaque (fibrous plaque and complicated plaque) again occurred with illumination in the wavelength range 314 nm to 334 nm. Conversely, the hard-calcified plaque class was most separable from the normal vessel class with illumination wavelengths longer than 380 nm. Since the best illumination wavelength ranges for soft plaques and hard calcified plaques were different, tissue identification was evaluated for the three-class case--normal artery versus soft plaques versus calcified plaques. Analysis with the generalized multiple-discriminant measure, a multiple-class extension of the Mahalanobis distance, indicated that illumination in the 300 nm to 314 nm range and the 400 nm to 458 nm range had the greatest three-class separability. Several multiple-class classifiers were also evaluated at each illumination wavelength. These classifiers did not reveal any wavelengths that were clearly best for accurate tissue-type identification. Finally, class separability and classification performance of combined features from multiple illumination wavelengths were also examined. The combination of features from multiple illumination wavelengths was found to increase separability and to improve the overall classification capability.

The optical measurement of primary mirrors for astronomical telescopes has become increasingly challenging for two reasons. The mirrors, in addition to being larger, are faster and more aspheric in order to shorten the length of the telescope, and the required accuracy of the optical surfaces is more stringent. This dissertation presents improved methods for measuring these mirrors in the laboratory to the required accuracy. The wire test and the scanning pentaprism test, which measure surface slope errors, were designed and run under computer control. The wire test was used to measure the conic constant of a 3.5-m f/1.75 primary mirror to an accuracy of ±0.003 and the scanning pentaprism test measured the conic constant of a 1.8-m f/1 primary to ±0.003. Improvements in these tests were identified that could increase the accuracy significantly. Interferometric optical testing with null correctors is widely used for measuring aspheric surfaces to high accuracy. A system-level analysis of the null test is given. The test is optimized for wavefront accuracy, imaging distortion, and measurement noise from ghost reflections and diffraction. The optical design and analysis of null correctors, including designs for testing 6.5-m f/1.25 and 8.4-m f/1.14 primary mirrors are given. Several new null corrector designs and a method for performing tolerance analysis using structure functions are given. An error in the null corrector, if not detected, would cause the primary mirror to be polished to the wrong shape. (The primary mirrors for the Hubble Space Telescope and the European New Technology Telescope were misshapen because of faulty null correctors.) A new test of null correctors is presented that uses a computer-generated hologram (CGH) to synthesize a perfect primary mirror. When the CGH is measured through the null corrector, it appears as a perfect primary mirror. Apparent surface errors in this measurement can be attributed to errors in the null corrector. A complete error analysis of this test is given. This method has been proven on null correctors for 3.5-m primary mirrors, where it measured errors as small as 5.1 nm rms and confirmed the conic constants to ±0.000078.

In this dissertation, the spectroscopic properties of thulium doped tellurite and thulium doped germanate glass are characterized. Absorption and emission spectra, lifetime, Fourier Transform Infrared Spectroscopy (FTIR), and thermo-gravimetric analysis are utilized to characterize the thulium doped tellurite bulk glass samples. Judd-Oflet theory, Fuchtbauer-ladenburg theory, Kushida's model, Burshtein's hopping model, Miyakawa's non-resonant energy transfer model are employed in ab-initio calculation of cross relaxation energy transfer. The fundamental mechanism of cross relaxation energy transfer is examined through ab-initio calculation and self-calibrating spectroscopy.Thulium doped tellurite glass microspheres are fabricated by spin casting technique. Single mode 2-mm laser is demonstrated from tellurite microsphere with high thulium doping concentration. General laser condition for self-terminating transition is discussed and concluded. Demonstration of 1.5-mm laser is achieved from a self-terminating transition of thulium doped in tellurite microsphere through a cooperative lasing technique.Highly efficient 1.9 micron fiber laser is demonstrated in thulium doped germanate fiber laser. The slope efficiency of the fiber laser is 58%, which indicates a quantum efficiency of 1.79. Single frequency laser operation at 1.9 micron has been successfully accomplished. A fiber based Fabry-Perot interferometer is utilized as a scanning filter to examine the single frequency operation. 4 W laser output has been achieved from a 40 cm long Tm-doped germanate double cladding fiber laser.

The Bismuth Silicon Oxide (BSO) single crystal can be obtained both in a large size and with good optical quality. It has been demonstrated that the BSO (Bi₁₂SiO₂₀) crystal is a practical holographic recording medium. BSO is a semiconductor and has a large electro-optic coefficient. These two properties of the BSO crystal are responsible for its capability to record. In this study, the linear and circular birefringence of the BSO crystal under an electric field were investigated. The measurement method is by passing a linearly polarized wavefield through the crystal. The transmitted wavefield is written in parametric expressions using Jones calculus, and the wavefield is probed by a simple ellipsometer. The two parameters in the Jones matrix, the linear and circular birefringence, are solved from the experimental data. The electro-optic coefficient is determined from the resulting linear birefringence to be 3.57 x 10⁻¹⁰ cm/V at λ = 632.8 nm. The diffraction efficiency and temporal response of the BSO crystal in the transverse electro-optic configuration were studied. The crystal was then coated with a single layer antireflection coating to investigate the effect of a multi-reflections inside the crystal. The result showed that although the visibility improved only about 20%, the diffraction efficiency and temporal response improved two times. The BSO crystal is used as the recording medium in a two-wavelength holographic interferometer. An optical edge filter is used in the interferometer to adjust the beam ratio, and a prism is used to incorporate tilt in the interferometer and to deviate the two wavelengths to satisfy the Bragg's condition for the volume hologram. The 488 and 514.5 nm lines of an argon-ion laser are used to give an equivalent wavelength of 9.45 μm. The interferograms obtained are of high contrast.

Photonic devices fabricated by ion exchange in glass have evolved to the point where conventional assumptions of waveguide symmetry and mutual independence are no longer valid. For example, during field-assisted ion exchange processes, the nonhomogeneity of ionic conductivity in the vicinity of the waveguide results in a time-dependent perturbation of the electric field. Previous studies have shown that the depth and vertical symmetry of buried waveguides are noticeably affected by the field perturbation. This Dissertation describes an advanced modeling tool for guided-wave devices based on ion-exchanged glass waveguides. A genetic algorithm is proposed to determine the physical parameters that drive the ion exchange process. The diffusion equation describing binary ion exchange is solved numerically. The effect of field perturbation, due not only to the conductivity profile, but also to the proximity of adjacent waveguides or partial masking during a field-assisted burial, is accounted for. A semivectorial finite difference method is then employed to determine the modal properties of the waveguide structures. The model is validated by comparison with a fabricated waveguide containing a Bragg grating. The modeled waveguides are utilized in the design of a multimode interference (MMI) device. A novel genetic algorithm-based design methodology is developed to circumvent issues with the commonly used self-imaging theory that arise when the MMI device operates in the regime of weak guiding. A combination of semivectorial finite difference modeling in two transverse dimensions and mode propagation analysis (MPA) in the propagation direction is used to evaluate the merit of each trial design. Two examples are provided of a 1 x 4 power splitter, which show considerable improvement in power imbalance and polarization dependent loss over that obtained by self-imaging theory.

Ion-exchanged ring resonators are presented as inexpensive yet highly sensitive integrated optic devices. Several historical applications for ring resonators are outlined then compared with competing technologies. The theory of ring resonator devices is described in detail. The optimum designs for both single and double arm ring resonator configurations are discussed. Ring resonator performance is shown to depend on both the waveguide propagation loss and coupling efficiency. A theoretical model of the ion exchange process is presented and used to determine the processing parameters that minimize bend loss. The coupling efficiency is then modeled for the theoretical waveguide profile. A fabrication recipe for producing high performance ring resonators is developed and the performance of several devices is analyzed. The applications of ring resonator devices for accurate measurement of waveguide birefringence and for rotation sensing are examined. A birefringence measurement technique using ring resonators is presented and the sensitivity of this method is compared to other approaches. The theoretical analysis of the rotational sensitivity of ion-exchanged ring resonator gyroscopes is presented and is shown to have an improvement of two orders of magnitude over previously reported ion-exchanged gyroscopes.

Nonlinear-optical switching and logic devices based on GaAs nonlinear Fabry-Perot etalons have been investigated theoretically and experimentally. The theoretical modeling has been performed with the first realistic and easily computed theory of GaAs nonlinear optical properties near the band edge. Both steady-state and dynamic calculations have been performed for optical bistability with GaAs etalons. High-transmission operation is predicted for certain etalon detunings from the excitation wavelength. Various logic-gate functions have simulated with the model. An investigation of differential energy gain in transient, one-wavelength operation was performed. The conclusion is that useful differential gain is not achievable in transient, one-wavelength operation if the pulse width is less than about ten times the carrier lifetime in the material. Waveguide structures with single-mode transverse confinement were designed and optical bistability was predicted for long GaAs etalons similar to cleaved waveguides. GaAs nonlinear optical devices were fabricated in forms of interest for application to optical parallel processing and guided wave signal processing. The fabrication work included etalon arrays and waveguide devices fabricated by reactive ion etching. The photolithography and reactive ion etching processes used and developed are described. Preliminary work on ultra-small quantum-confinement structures is described. Optical experiments were performed on the devices fabricated. The etalon arrays demonstrated extremely fast relaxation times for GaAs etalon devices, and demonstrated the ability to control material parameters through the fabrication process, by increasing the surface recombination rate of charge carriers. Fast optical bistability at low powers was also demonstrated in the array devices. Strip-loaded waveguides with cleaved ends were operated as optical bistable devices with conclusive evidence that the mechanism was electronic in origin. Nonlinear phase shifts of greater than $2\pi$ were observed in some waveguides. Such large nonlinear phase shifts are of great interest for the development of other nonlinear-optical waveguide devices.

A subaperture configuration to test aspheric optical components or systems is developed. The method developed has potential for testing rotationally symmetric aspheres without the use of null lenses. The aperture is divided into annular subaperture regions and an interferometer is refocused for each region to reduce the fringe density. Essential mathematical treatments involving annular subapertures, such as annular Zernike polynomials, are provided in detail. Numerical and experimental validations of the algorithm are described. Tolerance analyses on subaperture measurements are given. Computer programs were written to link the subaperture Zernike coefficients and to determine the full-aperture Zernike coefficients.