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Polarization-based Speckle Nulling Using a Spatial Light Modulator to Generate a Wide-field Dark Hole

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Title: Polarization-based Speckle Nulling Using a Spatial Light Modulator to Generate a Wide-field Dark Hole
Authors: Murakami, Naoshi Browse this author →KAKEN DB
Yoneta, Kenta Browse this author
Kawai, Kenya Browse this author
Kawahara, Hajime Browse this author
Kotani, Takayuki Browse this author
Tamura, Motohide Browse this author →KAKEN DB
Baba, Naoshi Browse this author
Issue Date: 1-Mar-2022
Publisher: IOP Publishing
Journal Title: The Astronomical journal
Volume: 163
Issue: 3
Start Page: 129
Publisher DOI: 10.3847/1538-3881/ac3510
Abstract: Direct detection of exoplanets requires a high-contrast instrument called a coronagraph to reject bright light from the central star. However, a coronagraph cannot perfectly reject the starlight if the incoming stellar wave front is distorted by aberrations due to the Earth's atmospheric turbulence and/or the telescope instrumental optics. Wave-front aberrations cause residual stellar speckles that prevent detection of faint planetary light. In this paper, we report a laboratory demonstration of a speckle-nulling wave-front control using a spatial light modulator (SLM) to suppress the residual speckles of a common-path visible nulling coronagraph. Because of its large format, the SLM potentially has the ability to generate a dark hole over a large region or at a large angular distance from a star of up to hundreds of lambda/D. We carry out a laboratory demonstration for three cases of dark hole generation: (1) in an inner region (3-8 lambda/D in horizontal and 5-15 lambda/D in vertical directions), (2) in an outer region (70-75 lambda/D in horizontal and 65-75 lambda/D in vertical directions), and (3) in a large region (5-75 lambda/D in both directions). As a result, the residual speckles are rejected to contrast levels on the order of 10(-8) in cases 1 and 2. In cases 2 and 3, we can generate dark holes at a large distance (up to >100 lambda/D) and with a large size (70 lambda/D square), both of which are out of the Nyquist limit of currently available deformable mirrors.
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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