Development of a cryogenic far-infrared post-dispersed polarizing fourier-transform spectrometer

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dc.contributor.authorBuchan, Matthew A.
dc.contributor.authorUniversity of Lethbridge. Faculty of Arts and Science
dc.contributor.supervisorNaylor, David A.
dc.contributor.supervisorSpencer, Locke Dean
dc.date.accessioned2024-08-09T19:21:12Z
dc.date.available2024-08-09T19:21:12Z
dc.date.issued2024
dc.degree.levelMasters
dc.description.abstractThe next generation of far-infrared space observatories will feature large (2 m to 3 m class), actively cooled (4.5 K) telescopes and high resolution spectroscopic capabilities provided by a Fourier-transform spectrometer (FTS). In the absence of telescope self-emission and with access to ultra-sensitive detectors, the multiplex advantage of an FTS becomes a disadvantage if instantaneous broad spectral measurements are attempted as the photon noise associated with the astronomical source now determines the spectral noise density. The only way to reduce the photon noise is by reducing the instantaneous spectral bandwidth observed by a single detector, typically to a fraction of one percent, using some form of post-dispersing element. While there are many approaches to post-dispersion, it is widely regarded that reflection diffraction gratings are the preferred method. The efficiency of a diffraction grating varies with wavelength. At the high angles of incidence required to achieve the necessary resolving power of R ∼ 100, reflection diffraction gratings operate with high and uniform efficiency (∼ 80%) for transverse magnetic (TM) polarized light, but lower and variable efficiency (10% to 40%) for transverse electric (TE) polarized light. The polarizing encoding properties of a Martin-Puplett interferometer can exploit this strong polarization dependence by ensuring that the interferometer output presents the TM mode to the grating. The hybrid post-dispersed polarizing Fourier transform spectrometer (PDPFTS) concept is the leading candidate for a future far-infrared astronomy mission. A fully cryogenic far-infrared PDPFTS has been developed in our laboratory to gain a better understanding of the challenges presented by this novel hybrid instrument. The results obtained from this PDPFTS will be valuable in guiding the development of such hybrid spectrometers being proposed for future far-infrared space observatories.
dc.embargoNo
dc.identifier.urihttps://hdl.handle.net/10133/6853
dc.language.isoen
dc.publisherLethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy
dc.publisher.departmentDepartment of Physics & Astronomy
dc.publisher.facultyArts and Science
dc.relation.ispartofseriesThesis (University of Lethbridge. Faculty of Arts and Science)
dc.subjectpost-dispersed polarizing Fourier-transform spectrometer
dc.subjectPDPFTS
dc.subjectLarge Facility Cryostat
dc.subjectreflection diffraction gratings
dc.subjectfar-infrared astronomy
dc.subject.lcshDissertations, Academic
dc.subject.lcshCryostats--Design and construction
dc.subject.lcshLow temperature engineering
dc.subject.lcshFourier transform spectroscopy
dc.subject.lcshFourier transform infrared spectroscopy
dc.subject.lcshInfrared astronomy
dc.titleDevelopment of a cryogenic far-infrared post-dispersed polarizing fourier-transform spectrometer
dc.typeThesis
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