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Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Baxter Womack. Vita. Includes bibliographical references.

Thesis (Ph.D.)--York University, 2005. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 231-232). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNR11640

The polarization dependent diffraction efficiency and imaging properties of high numerical aperture (N.A.) holographic optical elements (HOEs) were investigated to determine the suitability of these elements for magneto-optic data storage head applications. Two-wave first-order coupled wave theory was combined with a local planar grating model to determine the s and p-polarization diffraction efficiency characteristics of these HOEs. Experimental results for 0.55 N.A. focusing HOEs fabricated in silver halide photographic emulsions and dichromated gelatin films demonstrated that the p-to-s-polarization diffraction efficiency ratio at the Bragg angle corresponded with theoretical results to within 5%. Diffraction based wave propagation theory and a geometrical ray trace model were used to evaluate the imaging performance of these elements. Results from the diffraction based wave propagation model showed that the HOEs imaging performance had very minimal polarization dependence. The ray trace model indicated precise alignment and good wavelength stability are needed to achieve diffraction limited performance.

A detailed experimental and theoretical investigation of a magneto-optical trap for caesium atoms is presented. Particular emphasis has been placed on achieving high spatial number densities and low temperatures. Optimizing both of these together enables efficient evaporative cooling from a conservative trap, a procedure which has recently led to the first observations of Bose-Einstein condensation in a dilute atomic vapour. The behaviour of a magneto-optical trap is nominally determined by four independent parameters: the detuning and intensity of the light field, the magnetic field gradient and the number of trapped atoms. A model is presented which incorporates previous treatments into a single description of the trap that encompasses a wide range of its behaviour. This model was tested quantitatively by measuring the temperature of the cloud and its spatial distribution as a function of the four parameters. The maximum density was found to be limited both by the reabsorption of photons scattered within the cloud and by a reduction of the confining force at small light shifts. The nonlinear variation with position of the restoring force was found to be significant in limiting the number of atoms confined to a high density. A maximum density in phase space (defined as the number of atoms in a box with sides of dimension one thermal de Broglie wavelength) of (1.5 ± 0.5) x 10^-5 was observed, with a spatial density of 1.5 x 10¹¹ atoms per cm³. Cold collision losses from a caesium magneto-optical trap have been studied with the purpose of assessing their influence on spatial densities. In contrast to previous measurements of similar quantities, these measurements did not require the use of an ultra-low (< 10^-10 Torr) background vapour pressure. The dependence of the cold collision loss coefficient β on the trapping intensity was measured to permit identification of the different cold collision processes. The largest loss rates observed were those due to hyperfine structure-changing collisions, with a coefficient β = (2±1) x 10^-10cm³s^-1. A study is presented of a modified magneto-optical trap in which a fraction of the population is shelved into a hyperfine level that does not interact with the trapping light. In this so-called "dark" magneto-optical trap, improved densities of nearly 10¹²cm^-3 have been previously reported for sodium. The application of the technique to caesium is not straightforward due to the larger excited state hyperfine splittings. A simple theory for caesium is presented and its main predictions verified by measurements of density, number and temperature. A density of nearly 10¹²cm,^-3 was indeed obtained but at a temperature substantially higher than in the conventional magneto-optical trap.

Thesis (PhD)-Open University.

Graduation date: 1993

Design and operation of modular optical head for a magneto-optic test system are described. Alternate solutions to design problems are discussed. A 30mW semiconductor laser with an integrated 250MHz oscillator is selected. The oscillator is used to modulate laser read current for a reduction in laser feedback noise. A collimating lens with an appropriate focal length is chosen so the beam's truncation at the objective yields the maximum write power density. Astigmatism associated with the laser diode is reduced to 0.125 waves by defocusing the collimating lens and circularizing with an anamorphic prism pair. Head components are aligned within several minutes of arc by using alignment apertures and an autocollimator. Aberrations due to tilt between the disk and beam are examined and coma is found to be the major contributor.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Wei-Ping Huang. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Wei-Ping Huang. Includes bibliographical references. Also available online.