Deformable mirror-based pupil chopping for exoplanet imaging and adaptive optics

TL;DR

This paper introduces a novel deformable mirror-based pupil chopping technique for adaptive optics systems, improving correction of residual aberrations in ground-based telescopic imaging, especially for exoplanet detection.

Contribution

The paper presents a new focal plane wavefront sensing method using deformable mirror modulation to correct non-common path aberrations in AO systems.

Findings

Validated through simulations and laboratory testing

Achieves linear response with low DM stroke for low-order modes

Enables real-time correction at potentially kHz speeds

Abstract

Due to turbulence in the atmosphere images taken from ground-based telescopes become distorted. With adaptive optics (AO) images can be given greater clarity allowing for better observations with existing telescopes and are essential for ground-based coronagraphic exoplanet imaging instruments. A disadvantage to many AO systems is that they use sensors that can not correct for non-common path aberrations. We have developed a new focal plane wavefront sensing technique to address this problem called deformable mirror (DM)-based pupil chopping. The process involves a coronagraphic or non-coronagraphic science image and a deformable mirror, which modulates the phase by applying a local tip/tilt every other frame which enables correcting for leftover aberrations in the wavefront after a conventional AO correction. We validate this technique with both simulations (for coronagraphic and non-coronagraphic images) and testing (for non-coronagraphic images) on UCSC's Santa Cruz Extreme AO Laboratory (SEAL) testbed. We demonstrate that with as low as 250 nm of DM stroke to apply the local tip/tilt this wavefront sensor is linear for low-order Zernike modes and enables real-time control, in principle up to kHz speeds to correct for residual atmospheric turbulence.