Demonstration of simultaneous PIAA-coronagraphy and wavefront sensing using a single metasurface-based focal-plane optic
Abstract
Controlling the residual wavefront aberrations downstream of an extreme adaptive optics (ExAO) system is one of the main challenges in high-contrast imaging. The residual aberrations produce quasi-static speckles, mainly due to the difference between the paths taken by the wavefront-sensing light and the science light after they split in an ExAO system. Highly sensitive wavefront sensors, such as Zernike wavefront sensors (ZWFSs), are used as second-stage correctors to mitigate these non-common path aberrations. They are implemented as focal-plane optics in the science path. High-performing coronagraphs, such as complex mask coronagraphs (CMCs), are also implemented in the focal plane. They also provide a small (≲ 1.5 λ/D) inner working angle compared to other coronagraphs. Both have been shown to perform better when used with lossless apodization such as phase-induced amplitude apodization (PIAA) optics. Hence, it is natural to combine the two functionalities into a single focal-plane optic. Metasurfaces can be designed to have chromatic responses, and hence they can be used to realize such a focal-plane optic with different functionalities in different wavelength bands. We demonstrate the viability of such an optic by manufacturing a hybrid metasurface that is designed to function as a CMC and a ZWFS in two intermediate-band filters in the H band, each with a fractional bandwidth of approximately 1%. Specifically, we show the measured optical responses at different wavelengths in the band, demonstrating different phases with ∼ π/2 at shorter wavelengths and π at longer wavelengths between 1500 and 1700 nm. This would allow for wavefront sensing at the shorter wavelength of ∼ 1500nm and coronagraphy at the longer wavelength of ∼ 1700 nm. Additionally, we tested the mask on-sky with the MagAO-X instrument at the Magellan Clay 6.5 m telescope at Las Campanas Observatory, Chile. On-sky results show a contrast of ∼ 10−1 at a non-ideal wavelength of ∼ 1600 nm. This is comparable to the contrast curves from the simulated performance using the optical responses obtained from metrology around that wavelength. Finally, we evaluated the wavefront-sensing performance of the fabricated metasurface using the MagAO-X internal source at 1300nm and compared it with simulations. The measured reconstruction error is consistent with simulations of an ideal Zernike wavefront sensor, confirming the wavefront-sensing functionality of the metasurface.
Authors 25
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Affiliation as printed
Leiden Univ. (Netherlands)
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Leiden University · University of Arizona
Affiliation as printed
Leiden Univ. (Netherlands)
The Univ. of Arizona (United States)
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University of California, Santa Barbara
Affiliation as printed
Univ. of California, Santa Barbara (United States)
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Affiliation as printed
Leiden Univ. (Netherlands)
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University of California, Santa Barbara
Affiliation as printed
Univ. of California, Santa Barbara (United States)
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Affiliation as printed
Leiden Univ. (Netherlands)
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Affiliation as printed
Leiden Univ. (Netherlands)
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Affiliation as printed
The Univ. of Arizona (United States)
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Affiliation as printed
The Univ. of Arizona (United States)
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Affiliation as printed
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Affiliation as printed
The Univ. of Arizona (United States)
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Affiliation as printed
The Univ. of Arizona (United States)
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University of Arizona · National Astronomical Observatory of Japan
Affiliation as printed
Subaru Telescope, National Astronomical Observatory of Japan (United States)
The Univ. of Arizona (United States)
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Northrop Grumman (United States)
Affiliation as printed
Northrop Grumman Corp. (United States)
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Affiliation as printed
The Univ. of Arizona (United States)
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Affiliation as printed
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Affiliation as printed
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Affiliation as printed
The Univ. of Arizona (United States)
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Affiliation as printed
Flatiron Institute (United States)
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Affiliation as printed
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Affiliation as printed
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Affiliation as printed
Draper Lab. (United States)
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Affiliation as printed
Starfire Optical Range, Kirtland Air Force Base (United States)
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Affiliation as printed
Wyant College of Optical Sciences, The Univ. of Arizona (United States)
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Affiliation as printed
Durham Univ. (United Kingdom)
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