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.

Nd:YAG, well known for its operation at 1064nm, has a weaker transition at 946nm, whose lower level is thermally populated. This dissertation describes the design and development of a diode pumped, room temperature, quasi-four-level laser operating at the 946nm transition of Nd:YAG. The design addresses two primary issues in obtaining an efficient, high energy oscillator at 946nm. These are the ground state reabsorption losses due to the thermally occupied lower laser level, and the population inversion losses incurred at the much stronger 1064nm, transition. With 55 mJ in the normal mode, and 25 mJ in the q-switched mode, the output energies obtained are the highest energies per pulse reported to date for a diode pumped, 946mn Nd:YAG laser. A quasi-four-level laser theory is developed and used to optimize oscillator parameters affected by the thermally occupied lower laser level. The laser material length and the folded V shaped cavity are selected to maximize the gain per round trip in the cavity. The availability of stacked and microlensed diode array bars, along with an efficient pump coupling technique, allows the use of an end pumped configuration which provides the high pump density required to reach threshold in quasi-four-level lasers. The oscillator design was further refined to eliminate possible parasitic lasing paths and minimize amplified spontaneous emission losses at the 1064nm, transition. A large diameter laser disk with a Samarium doped cladding, which absorbs the 1064nm, radiation, reduces the number of 1064nm, ASE paths which deplete the inversion density in the pumped volume. The cladding significantly improves the storage efficiency, and hence the q-switched efficiency, of the oscillator. Although the oscillator was developed specifically for remote sensing of atmospheric water vapor, other applications can also benefit from the development of an efficient 946nm laser source. When frequency doubled, this wavelength allows access to the blue, which is highly desirable for high density data storage, displays, biological applications, and underwater communications.

The primary objective of this dissertation is to present a clear physical picture and useful insights of polarization effects in the diffraction of focused beams by grooved, multilayer-coated disks. The reading process of optical disk systems significantly relies on the reaction of the incident focused beam to the disk structure, may it be the groove profile or coating materials. The resulting complex-amplitude from diffraction is the main source for the readout signal. In the presence of the periodic pattern and the focused beam, however, different polarization states usually result in different complex-amplitudes. A good understanding of polarization effects in grooved multilayer disks is thus required for the optimum design of optical data storage systems. The pursuit of high-density recording inevitably drives the optical data storage industry to reduce the wavelength of light sources, decrease the track pitch of optical disks, and increase the numerical aperture of objective lenses. The track pitch and the size of the focused spot gradually approach the optical wavelength. Under these circumstances, the analysis of the interaction of focused beams with this type of high-frequency periodic disk using conventional scalar diffraction theory is no longer adequate. Only through vector diffraction study of polarization effects in the interaction of the focused beam with the periodic pattern can the characteristics of an optical disk system be fully understood and improved. Starting from the introduction of various polarization effects in optical disk systems and basic concepts of both scalar and vector diffraction theory, we then focus on the studies of diffraction patterns at the exit pupil of the objective lens and on the disk surface. Different behavior on the baseball pattern and in the effective groove depth is observed for the two polarization states. The use of the solid immersion lens to extensively increase the area density of optical disk systems prompts us to investigate the influence of evanescent-wave coupling on the near-field optical disk system. Finally, we study the feasibility of using a novel differential polarization microscope to reduce polarization effects and to increase the image contrast of magnetic domains on magneto-optical disks.

This dissertation describes advances in the photorefractive dynamic response, and in the understanding of response limitations. In a PVK/ECZ based composite using a tolane chromophore and TNFDM sensitization, a photorefractive response time constant of 4 ms was observed at an applied field (Eₐ) of 95 V/μm with a writing fluence of 0.5 W/cm², while the birefringence response time was under a millisecond. This showed that the chromophore orientational response does not limit speed, and suggests further investigation of photogeneration and transport processes to improve dynamic response. Another segment of research investigated performance changes by exposure under working conditions. Photorefractive properties for composites using chromophores of varied ionization potential (I(p)) were characterized as a function of exposure at Eₐ = 80 V/um, up to 10⁴ J/cm² total optical field exposure. The response time and photoconductivity were found to fatigue for all samples, but a higher chromophore I(p) was correlated to greater stability. The four-wave mixing dependence upon E a showed a variation in trap density with exposure which verifies the role of the C₆₀ anion, the ionized sensitizer, as a photorefractive trap. The third segment of research was the proof-of-principle of a photorefractive injection molding process. Photorefractive properties of molded materials were verified by four-wave mixing and two-beam coupling measurements. At Eₐ = 95 V/μm a diffraction efficiency of 25-30% and a gain coefficient near 50 cm⁻¹ was observed. This shows industrial processing potential of these materials and provides a path from hand crafted devices to mass-production techniques, promoting commercial acceptance.

Several topics concerning the imaging properties of patterned multilayer mask structures are addressed. Using the split-step beam propagation method in conjunction with linear systems theory, the reflected electric field from a patterned multilayer structure is calculated. This calculation accounts for the finite thickness of the pattern structure and the angular dependence of the multilayer reflector. A coherence mapping relationship is developed for a patterned multilayer structure placed in the object plane of an optical system. It is shown that both the spatial period of the pattern structure as well as the angular dependence of the multilayer reflector determines when a simulation must include angular dependence in the coherence mapping. If the illumination system is non-telecentric, a spatially dependent variation of the image irradiance occurs over the field of view of the optical system. A source with a finite spectral bandwidth causes a substantial irradiance decrease in the final image, due to the spectral dependence of the multilayer structure. In an effort to analyze the effects of roughness in short-wavelength imaging systems, the theory of speckle in partially coherent imaging systems is expanded to include the effects of a pattern structure, as well as imaging system aberrations. Including a pattern structure causes the partially developed speckle to manifest itself as a line edge roughness (LER) in images printed in a binary photoresist. It is shown that the LER can increase as the system becomes more incoherent. It is also shown that defocus causes LER produced in the image plane to dramatically increase. An iterative algorithm is developed to calculate the reflected electric field from a rough multilayer structure, which uses no first-order phase approximation and includes the effects of diffraction within the structure. The iterative algorithm is used with the coherence theory developed in this dissertation to analyze the imaging properties of a patterned multilayer structure. Including the effects of the multilayer structure and the thick pattern in the simulation results in an increase in LER, a slight shift in the ideal focus position and an asymmetry in LER for off-axis illumination.

Randomly inhomogeneous media, such as a turbulent atmosphere, degrade images taken by optical systems. This imposes strong limitations on the resolution achieved by optical systems. The quest for increasing the angular resolution of terrestrial telescopes is still open. This work is a small contribution in that quest. A problem of blind deconvolution arises when one attempts to restore a short-exposure image that has been degraded by random atmospheric turbulence. The image division method attacks this problem by using two short-exposure images of the same object and taking the ratio of their respective Fourier transforms. The result is the quotient of the unknowns transfer functions. The latter are expressed as Fourier series in corresponding point-spread functions. Cross multiplying the division equation gives a system of linear equations with the point-spread functions as unknowns. It is found that the system of linear equations, resulting from the implementation of the image division method, has a multiplicity of solutions. Moreover such system of equations is poorly conditioned. This brings the necessity of a regularization approach. This dissertation describes the development and implementation of a regularization algorithm for the image division method. Using this regularization algorithm the blind deconvolution problem is posed as a constrained least-squares problem. A least-squares solution is found by computing a QR factorization of the system matrix. The Householder transformation method is used to find this factorization. The QR decomposition transforms the problem into an upper-triangular system of equations which is solved by backsubstitution. Prior partial knowledge about the point-spread functions and the object (such as finite support and positivity) is used to impose constrains on the solution, solving the multiplicity-solutions problem. The regularization algorithm is tested with simulated and real data. Good quality reconstructions are obtained from the implementation of the regularized image division method on computer simulated atmospheric degraded images corrupted with up to 5% of additive Gaussian noise, or corrupted with Poisson noise with 100 or more photons as the average number of photons per pixel. It also yields good results when tested with real infrared short-exposure images.

The ability of optical systems to obtain images of desired objects is sometimes limited by the presence of background radiation. The background radiation can arise from scattering, self-radiation, or out-of-focus images, all originating from regions axially displaced from the object plane of interest. Techniques such as confocal microscopy, computer image reconstruction, various holographic techniques, and timegating tomography are all being developed in order to address the problem. Some of the prior techniques have been successfully applied in various fields where the imaging problem is encountered. All of the prior techniques have some advantages and some disadvantages. Recently, a new technique of background compensation has been proposed that utilizes controlled phase shifts in the pupil plane of the imaging instrument to distinguish in-focus radiation from background radiation. The new technique can potentially offer several advantages over the prior techniques, and may be applicable in situations for which no other technique is suitable. The present work describes the technique and reviews some relevant theoretical aspects and theoretical predictions for the technique. In addition, an experiment to test the basic concepts of the technique is described. The experiment consists of several discrete phases, and the results of the experiment are compared to the theoretical predictions. The results of each phase of the present experiment support the theoretical expectations for the technique, and it is concluded that the technique should be further investigated. The technique appears to represent a novel and potentially far-reaching alternative method by which the problem of imaging in the presence of undesired background radiation can be successfully addressed.