Laboratory Demonstration of Real-Time Focal Plane Wavefront Control of Residual Atmospheric Speckles

TL;DR

This paper demonstrates a real-time focal plane wavefront control algorithm called FAST, which significantly improves contrast in high contrast imaging by suppressing atmospheric speckles on the SEAL testbed.

Contribution

The paper presents the first experimental validation of FAST, a novel algorithm enabling millisecond-scale wavefront control to reduce atmospheric speckles in exoplanet imaging.

Findings

Achieved up to 5x contrast improvement with FAST.

Demonstrated effective control of residual atmospheric turbulence.

Operated successfully at 20 millisecond timescales.

Abstract

Current and future high contrast imaging instruments aim to detect exoplanets at closer orbital separations, lower masses, and/or older ages than their predecessors. However, continually evolving speckles in the coronagraphic science image limit contrasts of state-of-the-art ground-based exoplanet imaging instruments. For ground-based adaptive optics (AO) instruments it remains challenging for most speckle suppression techniques to attenuate both the dynamic atmospheric as well as quasi-static instrumental speckles on-sky. We have proposed a focal plane wavefront sensing and control algorithm to address this challenge, called the Fast Atmospheric Self-coherent camera (SCC) Technique (FAST), which in theory enables the SCC to operate down to millisecond timescales even when only a few photons are detected per speckle. Here we present the first experimental results of FAST on the Santa Cruz Extreme AO Laboratory (SEAL) testbed. In particular, we illustrate the benefit of ``second stage'' AO-based focal plane wavefront control, demonstrating up to 5x contrast improvement with FAST closed-loop compensation of evolving residual atmospheric turbulence -- both for low and high order spatial modes -- down to 20 millisecond-timescales.