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Proceedings Paper

Design, fabrication, and testing of stellar coronagraphs for exoplanet imaging
Author(s): Justin M. Knight; John Brewer; Ryan Hamilton; Karen Ward; Tom D. Milster; Olivier Guyon
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Paper Abstract

Complex-mask coronagraphs destructively interfere unwanted starlight with itself to enable direct imaging of exoplanets. This is accomplished using a focal plane mask (FPM); a FPM can be a simple occulter mask, or in the case of a complex-mask, is a multi-zoned device designed to phase-shift starlight over multiple wavelengths to create a deep achromatic null in the stellar point spread function. Creating these masks requires microfabrication techniques, yet many such methods remain largely unexplored in this context. We explore methods of fabrication of complex FPMs for a Phased-Induced Amplitude Apodization Complex-Mask Coronagraph (PIAACMC). Previous FPM fabrication efforts for PIAACMC have concentrated on mask manufacturability while modeling science yield, as well as assessing broadband wavelength operation. Moreover current fabrication efforts are concentrated on assessing coronagraph performance given a single approach. We present FPMs fabricated using several process paths, including deep reactive ion etching and focused ion beam etching using a silicon substrate. The characteristic size of the mask features is 5μm with depths ranging over 1μm. The masks are characterized for manufacturing quality using an optical interferometer and a scanning electron microscope. Initial testing is performed at the Subaru Extreme Adaptive Optics testbed, providing a baseline for future experiments to determine and improve coronagraph performance within fabrication tolerances.

Paper Details

Date Published: 12 September 2017
PDF: 11 pages
Proc. SPIE 10400, Techniques and Instrumentation for Detection of Exoplanets VIII, 104000N (12 September 2017); doi: 10.1117/12.2273558
Show Author Affiliations
Justin M. Knight, The Univ. of Arizona (United States)
John Brewer, The Univ. of Arizona (United States)
Ryan Hamilton, The Univ. of Arizona (United States)
Karen Ward, The Univ. of Arizona (United States)
Tom D. Milster, The Univ. of Arizona (United States)
Olivier Guyon, The Univ. of Arizona (United States)
National Astronomical Observatory of Japan (Japan)

Published in SPIE Proceedings Vol. 10400:
Techniques and Instrumentation for Detection of Exoplanets VIII
Stuart Shaklan, Editor(s)

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