Exploitation of the imaging capabilities of the new generation of ground-based astronomical telescopes relies heavily on Adaptive Optics (AO). Current AO system designs call for sodium guide star lasers capable of producing at least eight Watts of power tuned to the peak of the sodium D₂ line, with a high duty cycle to avoid saturation, and with 0.5-1.0 GHz spectral broadening. This work comprises development and testing of six candidate laser systems and materials which may afford a path to achieving these goals. An end-pumped CW dye laser producing 4.0 Watts of tuned output power was developed and used to obtain the first accurate measurement of sodium layer scattering efficiency. Methods of optimizing the laser output through improving pump overlap efficiency and reducing the number of intracavity scattering surfaces are covered. The 1181 nm fluorescence peak of Mn⁵⁺ ion in Ba₅(PO₄)₃Cl could be tuned and doubled to reach 589 nm. While efforts to grow this crystal were under way, the Mn⁵⁺ ion in natural apatite (Ca₅(PO₄)₃F) was studied as a potential laser material. Fluorescence saturation measurements and transmission saturation are presented, as well as efforts to obtain CW lasing in natural apatite. A Q-switched laser color-center laser in LiF : F⁻₂ was developed and successfully tuned and doubled to the sodium D₂ line. Broad-band lasing of 80 mW and tuned narrow-band lasing of 35 mW at 1178 nm were obtained with 275 mW of input pump power at 1064 nm. The measured thermal properties of this material indicate its potential for scaling to much higher power. A Q-switched intracavity Raman laser was developed in which CaWO₄ was used to shift a Nd:YAG laser, the frequency-doubled output of which was centered at 589.3 nm. To obtain light at 589.0 nm, a compositionally tuned pump laser of Nd : Y₃Ga₁.₁Al₃.₉O₁₂ was produced which generated the desired shift, but was inhomogeneous broadened, limiting the tunable power of the material. Finally, temperature tuning of a Nd:YAG laser was demonstrated in which the laser emitted up to 8.6 Watts at a temperature of -21.5 C, bringing the wavelength into a regime favorable for efficient Raman shifting by CaWO₄.

This study investigates various properties of titanium oxide thin films. The samples are prepared by electron-beam evaporation of the Ti₂O₃ material in an oxygen environment. Papers about the vaporization study of the titanium-oxygen system are reviewed; special attention is paid to the congruent vaporization in the titanium-oxygen system. The occurrence of congruent vaporization in our coating system is discussed. The compositions of the films are identified by Rutherford Backscattering Spectrometry. The effect of water vapor and the substrate temperature on the oxygen contents in RBS measurements is discussed. The optical properties of the samples are measured. With the spectrophotometric measurements, the methods for deriving the optical constants of transparent and opaque films are developed. The absorption of the TiO₂ film is investigated, and the corresponding mechanisms are discussed. The envelope method is employed to find the optical band gap of the TiO₂ film. The electrical resistivity of the titanium oxide films are measured with the four-point probe method, and the phenomenon of metal to insulator transition is demonstrated. The tensile stresses in our titanium oxide films are examined with a Nomarski microscope. The grain boundary model is adopted to explain the influence of thickness and oxygen content on the stresses development in thin film. Molecular dynamics simulation is used to study the structure and the thermal expansion of titanium dioxide rutile.

This dissertation presents an investigation of the charge-carrier dynamics in highly excited III-V semiconductor compounds. More precisely, after femtosecond excitation the photoluminescence of the GaN and related materials based Nichia NLPB 500 blue-light emitting diode (LED) is temporally and spectrally resolved using streak-camera techniques. Emission spectra are gathered both at 20K and room temperature. In addition, the emission of a pure GaN film grown by metal organic chemical vapor deposition is studied and compared to the more complicated structure of the diode. In either case, two spectrally distinct emission bands are found. Both samples show a large emission close to the band edge of the material. For the LED, amplified spontaneous emission is found in this band under very high excitation. The time resolved data shows simple, almost exponential, decays independent of pumping power or lattice temperature except for the amplified spontaneous emission in LED. The second emission band is impurity related and very different for the two samples. In the LED, impurities are deliberately doped into the active region of the device to provide luminescence centers whereas the pure GaN film is not intentionally doped. The LED emission shows a two component decay that changes its time constant with pump power which is well explained with in a three-level rate-equation model with saturable intermediate state. In the case of the GaN film an exponential decay independent of excitation density is observed up to a certain pump power where a fast initial component appears. Furthermore, spectral-hole burning experiments are performed on GaAs/AlGaAs multiple quantum wells. A new measurement technique for precise investigations of temporal gain evolution is given and subpicosecond gain in type II multiple quantum wells is demonstrated. Additionally, the experimental evidence for phonon sidebands of spectral holes in cool electron-hole plasmas is presented and theoretically investigated based on the Boltzmann equation coupled to the semiconductor Bloch equations. The carrier-dephasing time is studied as a function of plasma temperature, and indication for a strong dependence of carrier-carrier scattering rates on the temperature of the plasma is given. The findings are explained in a simple picture of blocked scattering channels for cold plasmas.

A gallium doped extrinsic silicon (Si:Ga) photoconductive detector was tested for sensitivity and quickness of response. The developmental goal for this detector material was high speed operation without compromised detectivity (D*). The high speed, p-type infrared photoconductor, with photoconductive gain less than unity, was tested at 10.5 μm to determine an experimental value for the detectivity-bandwidth product of D*f* = 3.8 x 10¹⁸ cm-Hz³/²/W. Subsequently a theoretical model taking into account the optical absorption profile and majority carrier transport processes within the detector was developed which agreed with the experimental data.

A novel bar code scanner that uses plane diffraction gratings on a flat rotating disk as the means of flying-spot laser scanning is designed and implemented. The design incorporates diffraction gratings that provide large angles of diffraction so that the lines generated in the bar code target region have sufficiently large radii for scanning most bar codes. The rotational symmetry exhibited by diffraction from plane gratings with incidence perpendicular to the grating surface is advantageous for the scanner system. The feasibility of the design is demonstrated by a prototype scanner consisting of commercially available diffraction gratings, an off-the-shelf focusing lens, and supporting optomechanical structures and electrooptics. The design concept is further developed towards fabrication and implementation of a custom-designed diffractive disk that can be readily injection molded with state-of-the-art Compact Disk (CD) replication technology. A stigmatic single-element focusing lens is also designed for the scanner system. Recent developments in diffractive optics mastering and replication technologies provide the impetus for this thesis; the possibilities of high efficiency mastering and inexpensive mass-replication of diffractive elements are driven by the semiconductor industry and continue to blossom. The diffractive disk designed in this thesis, however, does push the limits of the new technologies. A significant effort in creating a diffractive master for subsequent replication using a gray-scale mask microlithographic technology is presented. The thesis work falls short of an adequate master for replication. However, alternative mastering techniques for continuation of the project are suggested.

An experimental investigation on the furnace and CO₂ laser densification of sol-gel derived SiO₂-TiO₂-Al₂O₃ planar optical waveguides was performed. Solutions containing equal mole fractions of tetraethoxysiline [Si(C₂H₅O)₄], titanium ethoxide [Ti(C₂H₅O)₄], aluminum tri-sec-butoxide [Al(C₄H₉O)₃] were used to spin films with a nominal 2:2:1 molar SiO₂-TiO₂-Al₂O₃ composition. Emphasis was placed on determining what effects the densification techniques had on film shrinkage, index change, crystallization and composition. Film shrinkage and refractive index change were found to be similar for both densification techniques. Fully dense, amorphous film were obtained with both methods. After densification, further heating caused titania crystalline phases to form with both processing techniques. However, anatase formed in the furnace fired films while rutile formed in the laser irradiated films.

We conducted a detailed study and comparative analysis of the Voyager UVS and PPS stellar occultations of the Uranian ring system. The primary objective of this study was the determination of the constraints on the sizes of the ring particles. The Voyager UVS and PPS occultations probed the epsilon and delta rings at significantly shorter wavelengths (0.11 μm and 0.27 μm, respectively) and at substantially different viewing geometries than a large number of existing Earth-based occultations. These differences combine to produce a unique mutual sensitivity among the UVS, PPS and Earth-based observations to the particle properties of the rings. Our results yield slight, but significant differences between PPS and UVS optical depths. We interpret these differences as wavelength dependent scattering due to a population of small particles in the mm to cm size range in epsilon and delta rings. The size distribution of particles in epsilon and delta rings were found to be similar, the main difference being the total number of particles. In contrast to studies at longer wavelengths, our results imply a relatively steep particle size distribution characterized by a power law of index 3 or greater.

<p> To determine the mechanical and optical response of diamond crystals at high stresses and to evaluate anisotropy effects, single crystals (Type IIa) were shock compressed along the [100], [110], and [111] orientations to ~120 GPa peak elastic stresses. Particle velocity histories and shock velocities, measured using laser interferometry, were used to examine nonlinear elasticity, refractive indices, and Hugoniot elastic limits of shocked diamond. Time-resolved Raman spectroscopy was used to measure the shock compression induced frequency shifts of the triply degenerate 1332.5 cm^-1 Raman line. </p><p> Longitudinal stress-density states for elastic compression along different orientations were determined from the measured particle velocity histories and elastic shock wave velocities. The complete set of third-order elastic constants was determined from the stress-density states and published acoustic data. Several of these constants differed significantly from those calculated using theoretical models. </p><p> The refractive index of diamond shocked along [100] and [111] was determined from changes in the optical path length along the direction of uniaxial strain. Linear photoelasticity theory predicted the measured refractive index along [111]. In contrast, the refractive index along [100] was nonlinear. The refractive indices for [110] compression were not determined, but the data showed evidence of birefringence. </p><p> The splitting and frequency shifts of the diamond Raman line were measured for shock compression along [111] and were in good agreement with predictions from prior shock work. Frequency shifts were also measured along [100] and [110] up to ~60 GPa, extending previous measurements. The anharmonic force constants determined from all shock compression measurements agree with the previous shock compression determinations. </p><p> Hugoniot elastic limits for diamond shock compressed along different orientations were determined from the measured wave profiles. The elastic limits for the three orientations were highest at ~90 GPa peak elastic stress, but decreased at the higher peak elastic stress. Shear strengths were determined from the measured elastic limits: shocked diamond was strongest for compression along [110] and weakest for compression along [111]. The shear strength dependence on shock propagation direction was correlated with the stress magnitude normal to the slip plane, which appeared to inhibit the onset of inelastic deformation. </p>

Surface relief refractive microlens arrays are designed and fabricated using two methods. In the first method lithographically patterned circular cylinders of photoresist are melted to form the spherical lens shape. In the second method the lens shapes are sculpted lithographically from photoresist using a variable transmission (grey-scale) mask made from high-energy-beam-sensitive (HEBS) glass. / The microlenses were characterised interferometrically. It was found that close to diffraction limited performance was achieved in the f/0.9 to f/2 range using the photoresist melting process, whereas diffraction limited performance was achieved using the grey-scale method in the f/1 to f/7 range using aspherical elements. / The grey-scale method was also used to fabricate a 64 level computer generated hologram of the logo of the Institut national d'optique (INO) in a single step.

<p> Using the unique properties of the interaction between intense, short-pulse lasers and nanometer scale van-der-Waals bonded aggregates (or 'clusters'), modulated waveguides in hydrogen, argon and nitrogen plasmas were produced and extreme ultraviolet (EUV) light was generated in deeply ionized nitrogen plasmas. A jet of clusters behaves as an array of mass-limited, solid-density targets with the average density of a gas. </p><p> Two highly versatile experimental techniques are demonstrated for making preformed plasma waveguides with periodic structure within a laser-ionized cluster jet. The propagation of ultra-intense femtosecond laser pulses with intensities up to 2 x10¹⁷ W/cm² has been experimentally demonstrated in waveguides generated using both methods, limited by available laser energy. The first uses a 'ring grating' to impose radial intensity modulations on the channel-generating laser pulse, which leads to axial intensity modulations at the laser focus within the cluster jet target. This creates a waveguide with axial modulations in diameter with a period between 35 &mu;m and 2 mm, determined by the choice of ring grating. The second method creates modulated waveguides by focusing a uniform laser pulse within a jet of clusters with ow that has been modulated by periodically spaced wire obstructions. These wires make sharp, stable voids as short as 50 &mu;m with a period as small as 200 &mu;m within waveguides of hydrogen, nitrogen, and argon plasma. The gaps persist as the plasma expands for the full lifetime of the waveguide. This technique is useful for quasi-phase matching applications where index-modulated guides are superior to diameter modulated guides. Simulations show that these 'slow wave' guiding structures could allow direct laser acceleration of electrons, achieving gradients of 80 MV/cm and 10 MV/cm for laser pulse powers of 1.9 TW and 30 GW, respectively. </p><p> Results are also presented from experiments in which a nitrogen cluster jet from a cryogenically cooled gas valve was irradiated with relativistically intense (up to 2 x 10¹⁸ W/cm²) femtosecond laser pulses. The original purpose of these experiments was to create a transient recombination-pumped nitrogen soft x-ray laser on the 2_p3/2 &rarr; 1_s1/2 (&lambda; = 24.779 &Aring;) and 2_p1/2 &rarr; 1_s1/2 (&lambda; = 24.785 &Aring;) transitions in H-like nitrogen (N⁶⁺). Although no amplification was observed, trends in EUV emission from H-like, He-like and Li-like nitrogen ions in the 15 &ndash;150 &Aring;spectral range were measured as a function of laser intensity and cluster size. These results were compared with calculations run in a 1-D fluid laser-cluster interaction code to study the time-dependent ionization, recombination, and evolution of nitrogen cluster plasmas. </p>