Dissertation Defense: Justin Knight "Complex mask coronagraphs for high-contrast imaging"

    Friday, October 2, 2020 - 2:00pm

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    Password: 202876


    There are 4,284 confirmed extra solar planets, or exoplanets, most of which have been discovered by inferring their existence from observing the stars they orbit instead of collecting light from them directly. However, directly imaging exoplanets can lead to characterizing valuable information about them: size constraints, orbit, and atmospheric composition if spectroscopic analysis is performed. The main challenges of direct imaging are suppressing starlight by at least several orders of magnitude close to the star where exoplanets are likely to be, and controlling and maintaining the stability of this "high-contrast" imaging scene for observation.

    To enable direct imaging of exoplanets, we introduce and examine the coronagraphic architecture known as a Phase-Induced Amplitude Apodization Complex Mask Coronagraph, or PIAACMC. We discuss the design, fabrication, and use of an achromatic phase-shifting focal plane mask, commonly referred to as a complex mask, to enable broadband performance of the PIAACMC architecture for the Subaru Coronagraphic Extreme Adaptive Optics instrument at the 8 meter Subaru telescope in Hawaii. We pay particular attention to the effect of fabrication errors on the performance of a complex mask, and demonstrate how wavefront control from a deformable mirror can help mitigate them.

    Our discussion culminates with a preliminary on-sky analysis of the PIAACMC, where we discuss next steps toward enabling high-contrast imaging with this coronagraph, the importance of wavefront sensing and control for addressing the second challenge of ensuring a coronagraph can do its job, and a future outlook of the PIAACMC.