First laboratory demonstration of real-time multi-wavefront sensor single conjugate adaptive optics

TL;DR

This paper demonstrates a novel real-time multi-wavefront sensor adaptive optics system combining Shack Hartmann and FAST sensors, achieving high-speed correction to improve exoplanet imaging contrast.

Contribution

It presents the first laboratory implementation of simultaneous first and second stage AO wavefront sensing with two sensors on a single system, advancing high-speed adaptive optics technology.

Findings

Achieved 200 Hz loop speed for multi-WFS AO control.

Demonstrated effective speckle noise reduction in laboratory conditions.

Showed potential for deployment on current and future telescopes.

Abstract

Exoplanet imaging has thus far enabled studies of wide-orbit ($>$10 AU) giant planet ($>$2 Jupiter masses) formation and giant planet atmospheres, with future 30 meter-class Extremely Large Telescopes (ELTs) needed to image and characterize terrestrial exoplanets. However, current state-of-the-art exoplanet imaging technologies placed on ELTs would still miss the contrast required for imaging Earth-mass habitable-zone exoplanets around low-mass stars by ~100x due to speckle noise--scattered starlight in the science image due to a combination of aberrations from the atmosphere after an adaptive optics (AO) correction and internal to the telescope and instrument. We have been developing a focal plane wavefront sensing technology called the Fast Atmospheric Self-coherent camera Technique (FAST) to address both of these issues; in this work we present the first results of simultaneous first and second stage AO wavefront sensing and control with a Shack Hartmann wavefront sensor (SHWFS) and FAST, respectively, using two common path deformable mirrors. We demonstrate this "multi-WFS single conjugate AO" real-time control at up to 200 Hz loop speeds on the Santa Cruz Extreme AO Laboratory (SEAL) testbed, showing a promising potential for both FAST and similar high-speed diffraction-limited second-stage wavefront sensing technologies to be deployed on current and future observatories, helping to remove speckle noise as the main limitation to ELT habitable exoplanet imaging.