Providing intense, contamination-free beams of rare isotopes to experiments is a challenging task. At isotope separator on-line facilities such as ISAC at TRIUMF, the choice of production target and ion source are key to the successful beam delivery. Due to their element-selectivity, high efficiency and versatility, resonant ionization laser ion sources (RILIS) gain increasingly in importance. The spectroscopic data available are typically incomplete in the region of excited- and autoionizing atomic states. In order to find the most efficient ionization scheme for a particular element, further spectroscopy is often required. The development of efficient laser resonant ionization schemes for yttrium and astatine is presented in this thesis. For yttrium, two ionization schemes with comparable relative intensities were found. Since for astatine, only two transitions were known, the focus was to provide data on atomic energy levels using resonance ionization spectroscopy. Altogether 41 previously unknown astatine energy levels were found.

An experimental study of the interaction between 10.59 μm C0₂-laser radiation and the plasma produced by that radiation on plane, massive targets in a vacuum, is described. The laser used was a TEA double discharge device, giving an in vacuo irradiance in the regime of 10¹² W/cm² with 50 ns FWHM gain switched pulses. The laser oscillator cavity was operated in both stable and unstable configurations. Particular emphasis was placed on the full diagnosis of the scattered light and experiments were, therefore, designed to investigate the spatial, temporal and spectral characteristics of this unabsorbed fraction. The irradiation conditions under which the experiments were performed were investigated by analysis of the far field energy distribution. High absorption of the incident radiation was inferred from the low reflectivity level, the fraction of the incident radiation scattered out- side the solid angle of the focusing lens being accounted for, using a novel collecting mirror, or by the use of calibrated burn paper. Thus a total reflection was measured for the first time. A simple model was developed to enable the classical absorption contribution to the total absorption to be estimated, and results indicated that inverse bremsstrahlung absorption would be an important process for the conditions pertinent to the interac- tion. The contribution of anomalous absorption and scattering processes was estimated. Predicted cold electron temperatures and density scale lengths from the model, agreed well with those determined experimentally without the need to invoke flux inhibition. The spectral composition of the backscattered radiation in the region of the fundamental was investigated, and measured spectra were successfully interpreted by considering the stimulated Brillouin scattering process, and the Doppler effect of the expanding plasma corona. In particular, the depen- dence of the parametric growth rate on electron density was investigated by numerical solution of the ion acoustic wave dispersion relation. The angular distribution of the backscattered radiation was determined using annular apertures in the backscattered beam and the distribution found to be non-isotropic. Interpretation was based upon the resonance absorption process in a non-planar plasma geometry and invoked the retro reflecting nature of the stimulated Brillouin scatter mechanism. To investigate the effect of wave refraction in the underdense plasma (exhibiting a continuous density profile), a compact and readily used ray-tracing routine was developed and applied to plasmas with planar, rippled and simple concave or convex iso-density contours.

Design and realization of a conventional carbon dioxide laser was performed. Gas composition and gas pressure effects on laser output power were studied. Effects of input electrical power and current on laser power were also investigated. Beam profiling of the laser beam was performed by pinhole method. Laser beam parameters like beam divergence, beam propagation factor were measured. These properties were extracted from focusing a laser beam in near field and performing a number of cuts across the beam cross-section and measuring the beam diameter at these points. Diameter measurements were obtained by knife edge method. Laser beam parameters were obtained for three different power laser beams in two axes across the beam. Found parameters were compared with regard to beam power and beam cross-section axis. Also possibility of using the obtained laser beam in material processing was investigated.

In this thesis, my main focus was to establish a novel composite-cavity fibre laser (CCFL) and to apply it in sensing, particularly in the hydrophone application. The CCFL that I have proposed is formed by writing three wavelength matched fibre Bragg gratings directly into a continuous length of doped fibre. I have also examined the relative advantages and disadvantages of interferometric and intensity-based hydrophone systems, and have established a hydrophone system that can be switched between the two modes of operation, by making use of digital signal processing. I have established a theoretical model to study the lasing and spectral characteristics of the CCFL. My analysis showed that whilst the CCFL have significantly different phase and threshold conditions from the common semiconductor diode lasers with external cavity, the CCFL also have mode-limiting properties that are often sought after. Through simulations, I was able to identify that a non-uniform straining scheme, that is, when one of the sub-cavities of the CCFL is restrained from strain, can improve the sensitivity with respect to existing single cavity fibre lasers, in both the frequency and intensity domains. My simulations also showed that the sensitivity of such a straining scheme can be optimised by tuning the reflectivity of the gratings, sub-cavity lengths, doping concentration and pump power. I have fabricated multiple CCFLs using the in-house grating writing facilities, and have experimentally assessed their power and spectral related lasing characteristics. Whilst having a significantly longer total cavity length compared to typical fibre lasers, the CCFLs demonstrated stable single longitudinal mode operation and narrow linewidth in the order for a few tens of kHz. Asymmetric output power and frequency as a result of unequal sub-cavity lengths were also examined. Finally, I conducted sensing experiments by applying the CCFLs in strain monitoring and intensity-based hydrophone. My results showed that the non-uniform straining scheme had significantly improved the intensity response of the CCFL, and that the acoustic pressure and frequency can be determined by directly sampling and applying Fourier transform to the output intensity of the fibre laser.

This thesis details the design and construction of an experiment to measure the radial distribution of laser gain in a cylindrical Helium-Neon laser gain tube. This distribution is important as it can effect the transverse mode structure of a running ring laser. Earlier theoretical models of the distribution were not supported by high quality experimental data and fail to take into account some physical processes. A resolution of 8 parts per million in gain and 50 μm in radial position has been achieved. Gain distributions have been measured and are shown to be well modeled by a 0th order Bessel function with first roots at the tube walls and a central dip depending on excitation power; except for the region very near to the tube walls where a very rapid increase in gain has been observed. Hydrogen has been identified by spectroscopic analysis as the primary constituent of gas contamination and cause of the long term reduction in gain of large ring lasers. Additional work has been done to detect a proposed non-classical Lense-Thirring field around a spinning lead superconductor. It was found that any effect is at least 20 times smaller than predicted. Techniques and tools for data acquisition programming have been reviewed focusing on difficulties with coupling of user interface and application logic, monolithicity, difficulties with scripting and algorithm implementation.

This thesis presents a study of a 1.6 metre square, helium-neon based ring laser gyroscope (denoted PR-1). This device is mounted on one of the internal walls of a high rise building. After optimisation a cavity Q of 2.9x10¹¹ and a sensitivity to rotation of approximately 10⁻³ of the background Earth bias was obtained. A detailed investigation of the single mode operating regime and multi-mode thresholds was undertaken and could be well accounted for with a simple model of the gain curves. A key feature of the operation of PR-1 is persistent longitudinal mode hopping. It is shown that by running the laser at selective high powers, one obtains CW mode locked operation thereby negating the influence of mode hopping and allowing for long time data acquisition. PR-1 was used to demonstrate oscillation of the Rutherford building on its second fundamental mode during an earthquake. In a separate investigation, a range of supermirrors were studied to determine the optimum configuration in a 4 by 4 metre ring laser. The set with the highest finesse prevailed despite the comparatively low light levels on the photo detectors. The geometric stability of the lasers was not found to be a significant factor.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Dec. 4, 2007). PDF text: xii, 80 p. : ill. ; 6 Mb. UMI publication number: AAT 3273191. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references (leaves 244-254). Online version available on the World Wide Web.

Univ., Diss.--Ulm. / Nebent.: Technologien für langwellige VCSEL. Literaturverz. S. 157 - 169.

Zugl.: Stuttgart, Univ., Diss., 2008. / Druckausg. bei Jost-Jetter, Heimsheim erschienen.