The butt-coupling of a Fabry-Perot semiconductor laser diode and a singlemode optical fiber was realized and characterized in the near field. A novel butt-coupling model was developed and found very effective in describing all physical phenomena that occur when the butt-coupling parameters are varied over a wide range. The strong external optical feedback to the laser diode cavity that is present at extremely-short separations between the laser diode and the fiber is advantageously used to realize an extremely-short external cavity laser diode. By varying the length of the external cavity, the operational characteristics of this external cavity laser diode are controlled in a predictable and repeatable manner; a wavelength tunable laser diode source based on this effect was developed and analyzed. Another realization of an extremely short external cavity tunable laser diode, based on a closely spaced external filter with variable characteristics, was demonstrated. A potential application of the butt-coupling technique for light collection in an optical recording head is discussed. The work presented here is a research tool that can be used to facilitate the design of extremely-short external cavity laser diodes, which in many ways are technologically novel.

A method to predict modal noise in short distance (30 m), high temporal bandwidth (hundreds of MHz) multimode optical links is proposed. In order to accommodate low cost, mechanical alignment, the link medium is modified from single mode fiber (used routinely in telecommunication systems) to multimode fiber. Modal dispersion in multimode fiber calls for a reduction in link length to preserve a relatively high temporal bandwidth. The source is a vertical cavity surface emitting laser (VCSEL), which is well suited for the high packaging density, high temporal bandwidth, and low power dissipation requirements of short distance optical communication systems. Coherence properties of several different types of VCSELs are experimentally examined with constant and modulated injection current with a bandwidth typical of that used in data communications systems. A fluctuation in the spatial irradiance output pattern of the VCSEL is identified as the dynamic component responsible for significant modal noise effects. The effect of finite system coherence length has been applied to the simulation process. The reduction in output fiber face speckle contrast, due to a broader source power spectrum and/or due to fiber modal dispersion with increasing fiber length, mitigates the effect of modal noise in the transmission link.

A theory, based on material parameters, is developed for colloidal-crystal Bragg filters. The coupling constant, for coupled-wave equations, is derived to produce filter spectra. The spectra are modified by convolving with a Gaussian function to represent crystal defects. Scattering losses are calculated to attenuate the out-of-band transmission. The theory is tested by comparing theoretical spectra with experimental spectra from colloidal-crystal Bragg filters fabricated with polystyrene and poly(methyl methacrylate) colloid spheres. A novel cell, for containing the colloidal crystal, is presented in addition to crystal growing techniques. Coupled-wave theory spectra are compared with experimental filter spectra for filters with variable colloid sphere diameters, filter thicknesses, liquid refractive indices, and Bragg wavelengths. Spectral comparisons are based on the notch bandwidth, optical density, and out-of-band scattering losses. The bandwidths agree to within one nanometer provided the criteria for the Rayleigh-Gans scattering approximation are satisfied. The optical densities correlate with spectrophotometer-measured optical densities. And, scattering losses correspond to within 10 percent for all material parameters. Thus, the coupled-wave theory is consistent with the data and provides an excellent tool for evaluating colloidal-crystal Bragg filter performance.

Munition development has always been driven by the necessity of delivering enough explosives to a targeted object to destroy it. Targets that are protected by steel reinforced concrete housings have become increasingly more difficult to destroy. Improvements must be made in munitions engineering design to either deliver more payload to the target or to make the weapon more potent. In most cases, due to aircraft weight limitations, the delivery of more payload is not an option. Therefore, improving the destructive power of a weapon of a given payload requires the use of more powerful explosives. However, when the potency of an explosive is increased, its sensitivity to premature detonation also increases. The characteristics of the metal casing containing the explosive contribute significantly to the weapon's detonation sensitivity. Casing experience significant heating during weapon penetration. This heating can cause the weapon to detonate before it reaches its target location. In the past, computer codes used to model detonating weapons have not taken heating into account in their performance predictions. Consequently, the theoretical models and the actual field tests are not in agreement. New models, that include temperature information, are currently being developed which are based on work done in the area of computational fluid dynamics. In this research, a remotely located, high-speed, infrared (IR) camera is used to obtain detailed measurements of the passive radiation from an object in an energetic environment. This radiation information is used to determine both the emissivity and the temperature of the surface of an object. However, before the temperature or emissivity was determined, the functional form of the emissivity was calculated to be an Mth degree polynomial with respect to wavelength dependence. With the advent of large, high-speed, IR detector arrays, it has now become possible to realize IR imaging spectrometers that have very high spatial resolution. The IR spectrometer system developed in this research utilized a large detector array to allow multiple spectral images to be formed simultaneously on the image plane. In conjunction with the correct emissivity model, this imaging IR spectrometer can determine temperature to within ±5 degrees Celsius. These experimentally verified temperature maps were then integrated into the newly developed computer models. This additional information will result in more accurate computer codes for modeling the energetic environment. In turn, this will allow the weapon designer to accurately optimize weapon performance with respect to different materials, geometries and kinetics.

Experimental data often contains curious and unexplained results. In the course of experimental investigations of Raman shifting and the Co:MgF₂ laser, results were obtained which would not have been expected from the typical theoretical picture. In the case of Raman shifting, the forward Stokes conversion was found to depend upon the pump bandwidth. Numerical modeling suggests that coupling between the Stokes directions may be the root cause of the phenomena. In the case of the Co:MgF₂ laser, the laser output was observed to have large amounts of spectral structure. This amount of structure should not be expected in a room temperature vibronically broadened laser. Further experiments point to adsorbed water vapor for the cause of the structure, and this hypothesis is supported by a numerical model. Additionally, a unique method for treating the effects of arbitrary gain distribution on the propagation of the lowest order laser cavity mode is expanded to cover new distributions and new coordinate systems. An extension to parametric gains is also made. The extensions are then used to predict unstable regions in real laser cavities. These instabilities are observed in diffraction calculations. Guidelines for observing this intriguing result are presented.

This dissertation addresses both fundamental aspects of the coherent exciton kinetics in single semiconductor quantum wells and more application-oriented aspects of the collective excitonic optical properties in quantum well Bragg structures. We use a bosonic theory to investigate the ultrafast coherent exciton dynamics after an optical excitation in a single semiconductor quantum well. It is shown that, on intermediate time scales, nonlinear mean-field interactions between excitons lead to a coherent, wave-like evolution in the momentum distribution of optically inactive excitons, which can survive for some time before dephasing sets in. Driven by two-exciton correlations, this coherent quantum kinetic effect bridges the well-known kinetics associated with optical excitation on the one hand and incoherent relaxation on the other. We also study more general dynamical properties of bosonic mean field systems with N-species of excitons (in a single semiconductor quantum well). We find that the momentum-conserving exciton mean field equations, including the coupling to external fields and fermionic corrections, have the dynamical structure su(N,N). We show that one can define a non-real generalized "Bloch vector" and a non-hermitian "density matrix" description, which allow us to explicitly obtain all the constants of motion associated with the su(N,N) symmetry. The many-body effects and correlations of excitons in a single quantum well are mainly induced by the Coulomb interactions. In the case of a semiconductor quantum well Bragg structure, the light induced coupling between different quantum wells also dramatically affects the excitons' behavior, especially through the collective excitations of excitons in the whole structure. We investigate the linear excitonic optical properties of the quantum well Bragg structure induced by the collective excitations using the transfer matrix approach. We show that the so called "intermediate band" (IB) created by the exciton resonance, which does not exist in conventional photonic crystals, can be used for the stopping, storing and releasing of light, which is important in information processing devices. We also discuss the compensation of the dispersive distortion in the light delay process through reversing the IB band structure. Other conceptual and practical issues such as the decay rate of the IB modes and the generalized anti-reflection coating are also investigated.

The use of surfaces other than spheres in optical systems has become increasingly practical due to advances in manufacturing technology. Two such alternate surface types are aspheres and diffractives. Aspheric surfaces are typically used to control the Seidel (and higher order) aberrations. Diffractive surfaces, because of their high dispersion, can be used in broadband systems to provide chromatic aberration correction as well. The aim of this work is to develop general statements about the application of aspheric and diffractive surfaces to photographic and digital imaging lenses. The use of such complex surfaces can reduce the number of elements in an imaging system while maintaining equivalent image quality. General rules regarding this design tradeoff are developed. The improvement in performance achieved by adding aspheric and diffractive surfaces, alone or in combination, to one, two and three element lenses is examined. A measure of performance is defined based upon the transverse ray errors calculated from real ray tracing. Using this, lenses of equal performance are designed for various combinations of numerical aperture and field angle. Contours of equal performance are compared for lenses of different constructional parameters. As an example application of the use of aspheric and diffractive surfaces, the design of an objective lens for a digital still camera is considered. Possible configurations for one, two and three element lenses are discussed. The use of diffractive surfaces in broadband imaging systems brings with it the associated cost of stray light due to the variation of diffraction efficiency with wavelength. Under the condition of a low contrast object, the effect of diffraction efficiency is included in the measure of performance and the systems containing diffractive surface reevaluated. The single axis symmetry of the aspheric or diffractive surfaces used results in the inability to remove surface to surface decenter in the lens element during the final edging process. The sensitivity of the systems containing aspheric surfaces to a decenter error is examined and compared to that of a conventional system.

Gamma-ray detectors based on high-density semiconductors, such as cadmium zinc telluride, are being developed for applications in nuclear medicine, astronomy and the monitoring of nuclear weapons material. In contrast to the more commonly used scintillators, which convert gamma-ray energy into light, semiconductors directly convert the energy of a gamma ray into electrical current. This direct conversion often leads to the perception that gamma-ray detection in semiconductors is not an estimation problem. This dissertation presents the contrasting view that gamma-ray detection in semiconductors is fundamentally an estimation problem, and it is only through the appropriate analysis of gamma-ray signals that optimal energy resolution and spatial resolution can be achieved. To estimate interaction parameters, such as the energy of the gamma ray and its interaction position, it is first necessary to have an accurate model of the detector system. In this work, the system consists of slabs of CdZnTe with arrays of pixel electrodes mounted on integrated readout circuits. A theoretical model of detector behavior is presented, including a new model for charge spreading in the detector. Methods for experimentally determining detector behavior are developed based on mapping detectors with narrow beams of gamma rays. Estimating the interaction positions and energies proceeds from a statistical model of the production of pixel signals, derived from our physical model. Energies and interaction positions are estimated by maximizing the likelihood function. The likelihood is the probability that a gamma ray with a given position and energy will produce an observed set of pixel signals. This maximum-likelihood estimation improves the energy resolution over simpler methods and can give the interaction position in three dimensions. A likelihood function can be calculated for an entire set of gamma rays, in which case an image can be estimated from the raw data without ever estimating individual interaction positions and energies. The Expectation-Maximization algorithm is used to reconstruct images and energy spectra by maximizing the ensemble likelihood function. In this work, the list-mode form of the algorithm is used, meaning that the raw data consist of lists of pixel signals for each gamma ray. Both spatial and energy resolution improve when this algorithm is applied to the raw pixel signals.

This dissertation develops a theoretical framework for guided mode resonance filters (GMRFs) with surface relief gratings based on a physical optics approach. A GMRF is a unique optical device that utilizes the resonance due to the coupling of a diffraction order of a grating with a waveguide mode. This coupling process leads to rapid fluctuations in the reflected and transmitted fields from the GMRF. The reflected output can change from 0% to 100% over extremely small wavelength (or angular) regions with a Lorentzian lineshape. It is shown that the surface relief gratings can be effectively modeled using effective medium theory (EMT). Combining the EMT modeled surface relief grating and thin film theory provides an approximation of the sidelobe levels around a resonance peak and can be used to design a grating that acts as an anti-reflection coating. In addition, EMT can be combined with multilayer waveguide relationships to provide an improved method for determining the wavelength of a resonance. The effect of a finite aperture grating upon the reflected and transmitted output from a GMRF is analyzed. The resonance peak width is found to be inversely proportional to the grating length and the peak efficiency of the GMRF is shown to decrease with reduced grating length. Finally, the design and analysis of a GMRF with a nonlinear waveguide is presented and shown to be capable of providing all-optical switching with low input intensities.

A new phase-shifting scatterplate interferometer is realized by exploiting the polarization characteristics of a birefringent scatterplate. Controlling the component of polarization that is scattered allows the birefringent scatterplate to separate the test and reference beams. The advantages of this design are that it does not require auxiliary optics to be placed near the surface under test and the "hot spot" and background irradiance, which are inherent to scatterplate interferometers, can be eliminated. This study provides a description of the phase-shifting birefringent scatterplate interferometer, expands the theoretical model of the scatterplate interferometer to include polarization and phase shifting, analyzes the performance of the new interferometer and discusses possible sources of error induced by the design. In addition, a few component specific topics are addressed. Two methods for generating the birefringent scatterplate are presented and the role the scatterplate plays in removing the "hot spot" is explored. Furthermore, the practicality of using a liquid crystal retarder for phase shifting is analyzed in the process of determining the performance of the interferometer.