Techniques for High Contrast Imaging in Multi-Star Systems I: Super-Nyquist Wavefront Control

TL;DR

This paper introduces Super-Nyquist Wavefront Control, a novel technique enabling high-contrast imaging of exoplanets in multi-star systems by controlling wavefront errors beyond the deformable mirror's usual correction zone, achieving contrasts of 5×10^-9.

Contribution

The paper presents the Super-Nyquist Wavefront Control method, allowing effective wavefront correction beyond the DM's nominal region for imaging planets in multi-star systems.

Findings

Achieved contrast of approximately 5×10^-9 using SNWC.

Demonstrated wavefront control beyond the DM's typical correction zone.

Enabled direct imaging of planets in binary/multi-star systems.

Abstract

Extra-solar planets direct imaging is now a reality with the deployment and commissioning of the first generation of specialized ground-based instruments (GPI, SPHERE, P1640 and SCExAO). These systems allow of planets $ 10 ^ 7 $ times fainter than their host star. For space-based missions (EXCEDE, EXO-C, EXO-S, WFIRST), various teams have demonstrated laboratory contrasts reaching $ 10 ^ { -10 } $ within a few diffraction limits from the star. However, all of these current and future systems are designed to detect faint planets around a single host star or unresolved multiples, while most non M-dwarf stars such as Alpha Centauri belong to multi-star systems. Direct imaging around binaries/multiple systems at a level of contrast allowing Earth-like planet detection is challenging because the region of interest is contaminated by the hosts star companion as well as the host Generally, the light leakage is caused by both diffraction and aberrations in the system. Moreover, the region of interest usually falls outside the correcting zone of the deformable mirror (DM) for the companion. Until now, it has been thought that removing the light of a companion star is too challenging, leading to the exclusion of binary systems from target lists of direct imaging coronographic missions. In this paper, we will show different new techniques for high-contrast imaging of planets around multi-star systems and detail the Super-Nyquist Wavefront Control (SNWC) method, which allows to control wavefront errors beyond nominal control region of the DM. Using the SNWC we reached contrasts around $ 5 \times 10 ^ { -9 } $ in a 10% bandwidth.