A new figure of merit, the potential information gathering power, P , is developed for use in evaluating the performance of spectrographs. It is based on the premise that it is desirable to maximize the product of the SNR at each resolution element in the reduced data by the number of resolution elements. Because of this general intent, it places no a priori emphasis on any particular scientific use. This figure is then applied to the task of improving the performance of a real fiber-fed astronomical spectrograph when it is operated in its high-resolution mode. It is shown that the optimum configuration corresponds to adding a new field lens, changing the focal length and size of the collimator, and arranging the camera and collimator axes to the narrowest allowable geometry. An approximate gain of between 15% to 18% may be realized.

The linear and nonlinear optical properties of semiconductor nano-structures and photoactive yellow protein (PYP) have been studied in this work. The reflection and transmission properties of multiple InₓGa₍₁₋ₓ₎As quantum well (QW) samples are first presented. Constructive interference in the reflection from the QWs is observed when the QWs are spaced by λ/2 (λ = exciton absorption peak wavelength) and destructive interference when the spacing is λ/4. The nonlinear transmission of fs pulses through a QW sample is also studied. A broadening of the exciton transition with negligible loss of oscillator strength is observed. Semiconductor microcavity samples with embedded quantum wells exhibiting normal mode coupling (NMC) are studied both in the linear and nonlinear regime, with ultrafast time resolution using upconversion. A decrease in the modulation depth of the NMC oscillations and reflection dips with increasing incident photon flux without a change of NMC oscillation period and splitting are observed, consistent with a bleaching of the exciton transition without loss of oscillator strength. The effective mass of multiple QW samples measured from the slope of Landau Levels of the QWs in magnetic field is measured for both photoluminescence (PL) and absorption spectra. For some samples, the absorption spectra show an effective mass consistent with the electron-hole effective mass while the PL spectra show an effective mass consistent with just the electron. This is explained by hole localization on monolayer island fluctuations on the QW/barrier interfaces. The magnetic field is also used to measure Faraday rotation in semiconductor microcavities exhibiting NMC. A resonant Faraday rotation of 3° degrees is observed in reflection. Finally the nonlinear one-photon and two-photon absorption (TPA) properties of PYP are investigated. One-photon excitation results in a complete bleaching of the absorption peak. No TPA is observed, but an upper limit of 3.5·10⁻⁵²cm⁴ s molecule⁻¹photon⁻¹ for the TPA cross section is found.

I have measured the refractive index of zinc selenide for wavelengths between 8 and 12 mum and temperatures from 85 to 300 K. Each measurement was made by finding the deviation angle of a beam perpendicularly incident on a right triangle prism. The resulting data curves are fitted to polynomials for the temperature dependence and to three different dispersion formulae for the wavelength dependence. I achieved accuracies in the refractive index of ±0.0008 and my results agree well with most previously available data. Refinements to the previously established experimental procedure and error analysis are also presented.

Over the past decade, circular grating surface emitting DBR lasers (CGSELs) have progressed from theory to reality. These devices possess several properties that make them attractive options for such applications as optical interconnects and laser arrays. These advantages include low divergence angles, circular beam profiles, and high power output. In this dissertation, the addition of new functionality to these lasers including wavelength tunability, focusing, beam steering and beam shaping is investigated. The theory governing device operation is presented. Pertinent discussions include the coupled mode equations, grating coupling, focusing and changes to the effective index of refraction resulting from current injection through a transparent electrode on the grating. The development and refinement of the device fabrication process is detailed. Key milestones in the grating writing process included achieving first order gratings (Λ = 0.15 μm), creating chirped period gratings for focusing and optimizing the linewidth and uniformity of the grating for high power devices. Of equal importance in obtaining high efficiency devices was the reactive ion etch process. Two different etch recipes were developed: one for mesa-definition and a shallower grating-defining etch. Significant evaluation of the electrical and optical properties of the transparent electrode, Indium Tin Oxide, was performed. Incorporating ITO into the fabrication process required optimization of deposition, patterning, etching and annealing. Device performance, efficiency and functionality improved with each generation. Consequentially, over 225 mW of output power for a injection current of 600 mA, or a slope efficiency of 0.43 mW/mA, was produced by the final generation of high power CGSELs. Focusing was demonstrated by the creation of individual devices with different focal lengths. Coarse mode selection was obtained by removing radial segments of the circular grating thereby eliminating both feedback coupling and surface outcoupling. Dynamic functionality such as beam steering and wavelength tuning was also realized for devices with ITO. Over 1° of beam steering was achieved for an ITO injection current of 35 mA. Similarly, over 1 nm of tuning, or 0.5 nm of continuous tuning, was accomplished. In conclusion, possibilities for improvements in device performance and future work are suggested.

Absolute radiometric calibrations of Landsat 5 Thematic Mapper satellite are improved with the inclusion of a method to invert optical depth measurements to obtain an aerosol particle size distribution and a non-lambertian surface reflectance model. Also, a program is developed to improve speed and standardization of the entire calibration procedure. The inverted size distributions can predict radiances varying from the previous jungian distributions by as much as 5 percent, though the reduction in the estimated error is less than one percent. An empirical model for the surface reflection of White Sands using a two-degree polynomial fit as a function of scattering angle was employed. The model reduced estimated errors in radiance predictions by up to one percent. Satellite calibrations dating from October, 1984 are reprocessed using the improved methods and a linear estimation of satellite counts per unit radiance versus time since launch is determined.

The light scattered from a scatterer depends on the geometrical properties such as size, shape, and their distributions as well as electromagnetic properties such as the complex index of reflection. The four major Mueller scattering matrix elements have been experimentally measured for an aluminum rough surface scattering laser light at lambda = 441.6nm for various incident angles. Measurements were also made for non-conducting diffuse surface and an aluminum coated diffuse surface. The sixteen Mueller matrix elements of these diffuse surfaces were measured in order to study the relative role of reflectance and roughness for scattering from a rough surface. Some representative matrix elements for the rough surfaces as well as for conducting and non-conducting rough surfaces are shown. S11 and S34 are sensitive to illumination angles and surface variation. S33 are sensitive to illumination angles only. S34 are very sensitive to the change of refractive index from real to complex.

The design, fabrication, and testing of diffractive microlens arrays for use in fiber optic interconnects is presented. Advantages of using diffractive microlenses for fiber interconnects instead of refractive microlenses are discussed. A theoretical discussion of diffractive lens operation including the effects of chromatic aberration on fiber coupling is given, along with equations for mask generation. From these equations, a set of masks to fabricate an array of four phase level diffractive microlenses was produced. Experimental procedures for the fabrication of diffractive microlenses from this mask set are presented. Arrays of binary lenses in photoresist with depth errors of less than 4% were fabricated and test results are given. A novel fiber optic tap utilizing both surface relief microlenses and a volume holographic element is demonstrated. In addition, a fiber array coupler using silicon V-grooves and an array of diffractive lenses is also demonstrated.

<p> Efficient nonlinear optical devices are designed and demonstrated in "photonic molecule''-like coupled-cavity resonator systems on a semiconductor chip. A coupled-cavity resonator may be designed to support distributed supermodes, and to allow independent control of the resonant frequency and linewidth of each supermode. Such control allows reduction of dispersion without compromising effective nonlinearity in the resonator, as well as the design of anisotropic output coupling or radiation that allows optimized nonlinear functions. Therefore this resonator manifests itself as a favorable platform for building nonlinear devices including optical parametric wavelength converters and oscillators based on four-wave mixing that call for different couplings to the signal, pump and idler modes. A physical model based on coupled-mode theory describes all relevant linear and nonlinear processes in triply-resonant microcavities, and a generalization of the usual nonlinear figure of merit is proposed to evaluate the effects of distributed supermodes on nonlinear conversion efficiency in such devices. Experimental work is presented that demonstrates coupled cavity devices for wavelength conversion in crystalline silicon, where two-photon absorption sets conversion efficiency limitations. In addition, an investigation of deposition conditions of hydrogenated amorphous silicon is described where amorphous silicon allows for a higher nonlinear figure of merit than crystalline silicon, promising increased performance in such devices. More generally, mode interference and coupling in coupled-cavity resonators, as a unique degree of freedom in integrated optics, is explored through designs of linear devices including efficient optical filters, wavelength converters, and modulators. </p>

Because of the calculational speed of the fast Fourier transform (FFT) calculational algorithm for computing the discrete Fourier transform (DFT) and the usually small number of discrete components necessary to represent the data and its restoration, discrete Fourier techniques have been found to be the most efficient for data enhancement and restoration operations. / The thrust of this research has been the development of fast and efficient procedures for determining the continued Fourier spectrum, or the continued interferogram for FTS data, with the application of as many of the pertinent physical constraints as possible. The inverse DFT is a Fourier series, and the coefficients of the sinusoids are the discrete spectral components. This Fourier series is added to the function formed from the low frequency band, (or to the interferogram for FTS data) and the sum of the squared error is minimized in the total function to produce a set of linear equations in these high frequency coefficients for the constraint of finite extent, and a set of nonlinear equations for the constraint of minimum negativity. A variation of the method of successive substitutions was adapted that is very efficient in solving the set of nonlinear equations. The procedure to implement the constraint of minimum negativity has been found to easily accommodate the constraints of finite extent and the minimization of values above an upper bound also, so that all these constraints may be simultaneously applied to a given set of data. Further, the procedure to implement the constraint of minimum negativity has proven very insensitive to noise error. / The above procedures for implementing the constraints of finite extent and minimum negativity have proven successful in the restoration of both simulated and experimental infrared spectroscopy data. For infrared grating spectroscopy data the data are first inverse filtered, then the constraints are applied to continue the Fourier spectrum. For FTS data, it is the interferogram that is continued. In certain cases the interferogram is pre-multiplied by a suitable window function before extension in order to reduce the artifacts. / Source: Dissertation Abstracts International, Volume: 43-03, Section: B, page: 0771. / Thesis (Ph.D.)--The Florida State University, 1982.

A spectral broadening of 1.3 $\pm$ 0.2 MHz was observed in laser light forward scattered through a solution of water and particulates. Laser light from a single mode argon-ion laser was collected after scattering through water with the addition of particulate matter. The collected light was analyzed with a diffraction grating, a Fabry-Perot spectrometer and a light mixing technique. The grating spectrometer measures spectra in the gigahertz range, the Fabry-Perot in the megahertz, and the mixing technique measures in the kilohertz range. The only non-null results were found with the Fabry-Perot spectrometer. Broadening was only observed when the added particles were smaller than the wavelength of the illuminating laser. The broadening is attributed to coupling between fluctuations in particle concentration and fluctuations in entropy. Entropy fluctuations exist in a pure fluid, although they are very weak in water. The presence of the particles induces entropy fluctuations (or temperature gradients) in the fluid which, in turn, induce fluctuations in particle concentration. / It was found that the best fit to the scattered spectra was a Voigt with a large Gaussian component. The coherence theory was extended to a multimode source. The fringe visibility versus path difference in a Michelson interferometer was calculated for single and multimode Gaussian and Lorentzian spectra. Data were taken with a multimode argon-ion laser coupled with a Michelson interferometer and compared to the theoretical calculation. The fringe visibility for the scattered, multimode laser matches the Gaussian multimode calculation. This may be a useful result for enhancing the capability of remote sensors. / Source: Dissertation Abstracts International, Volume: 56-08, Section: B, page: 4396. / Major Professor: David VanWinkle. / Thesis (Ph.D.)--The Florida State University, 1995.