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https://hdl.handle.net/2115/84771

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

英語

2022-03-01

IOP Publishing

The Astronomical journal

163(3)

129

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.

学術雑誌論文

Version of Record

0004-6256