Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 27.

Thesis (M.S.)--University of Wisconsin, 1964. / Bound typescript (Photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 14).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 48-49.

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This work describes a study of the propagation properties of a modified surface plasmon mode, and of the coupling properties of that mode using a grating coupler. The surface plasmon, a polariton involving coupling of electromagnetic waves to the plasma oscillations of a metal, is modified by the application of a dielectric overlayer to the interface between the metal and air. In the far infrared region of the electromagnetic spectrum, the overlayer causes dramatic changes in several properties of the mode, which can be verified by measuring the propagation length of the mode. Measurements at a wavelength of 118.8 μm of the propagation length as a function of the thickness of a polycrystalline silicon overlayer on silver showed that the mode has the expected properties. They also indicated that the Drude model of the dielectric function of the silver is valid at 118.8 μm, even when using established Drude parameters, which are based on measurements in the visible and near infrared region of the electromagnetic spectrum. The coupling study measured the fundamental coupling parameters, also at a wavelength of 118.8 μm, for coupling via a grating between free-space waves and the surface plasmon, and measured the effect of the overlayer on these parameters. Efficient coupling was achieved, but a theoretical treatment of the coupling system proved to be beyond the scope of first-order grating-coupler theory. This was true despite the fact that the grating amplitude was a small fraction of the wavelength, a common criterion for the application of such a theory. Several possible reasons for the breakdown of the theory were considered, but definite answers require additional experiments. The most prominent possibilities are the shape factor, and the depth of the grating compared to the penetration depth of the fields into the metal. Though not all the data is completely explained, the studies herein demonstrate that the overlayer eliminates many of the deficiencies which limit the generation and control of far-infrared surface plasmons.

The role of high infrared (IR) reflectance in the temperature regulation of a single species of cactus, Cereus giganteus (saguaro cactus), was investigated. Two independent methods were used to determine the effect of high near-IR reflectance on C. giganteus stem temperatures. The first method was to measure the surface temperature of two individual plants of comparable size and health, one of which was partially shaded by a canopy of loose sun-screening material. The second method involved the numerical solution on a computer of the energy balance, or heat transfer, equation for C. giganteus. High reflectance at near-IR wavelengths was found to decrease the peak surface temperature reached by C. giganteus by 3.2 to 3.3°C. This figure is valid for the fairly mild environmental conditions encountered in the Sonoran Desert at an altitude of 940 m during late September and early October.

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