Jerry Clark (Committee Member), Jason Deibel (Committee Member), Gregory Kozlowski (Committee Member), Douglas Petkie (Advisor)
Master of Science (MS)
This thesis is a study of the propagation of millimeter wavelength (MMW) and submillimeter wavelength (sub-MMW) electromagnetic radiation (a.k.a. THz radiation) through the Earth's atmosphere. THz radiation is electromagnetic radiation that exists between the microwave and far infrared regions of the electromagnetic spectrum. It is nonionizing radiation but can penetrate through materials that are opaque to visible light so therefore has many new and useful applications. Unfortunately, THz radiation is heavily attenuated by the Earth's atmosphere as it propagates through it. This therefore represents a challenge to communications and sensing applications at millimeter and sub-millimeter wavelengths. In this work, the general theory of how the atmosphere attenuates propagating THz radiation by absorption and scattering is discussed. From this discussion, we find that water vapor is the constituent of the Earth's atmosphere most responsible for the absorption of THz radiation. The absorption of THz radiation by water vapor was measured at 325 and 620 GHz using steady state or frequency domain absorption spectroscopy. The absorption lines of these frequencies lie in the far wings of a very strong water absorption line at 557 GHz. Spectral line shapes were recorded across a range of pressures and fitted to Voigt profiles. The resulting relationship between the line width and pressure was shown to be linear and very close to published values. Finally, transient signals associated with population and polarization relaxation times were measured at 325 GHz using transient or time domain spectroscopy techniques. Experimental results associated with the steady state and transient measurements will be presented and discussed.
Department or Program
Department of Physics
Year Degree Awarded
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