First on-sky demonstration of spatial Linear Dark Field Control with the vector-Apodizing Phase Plate at Subaru/SCExAO

Abstract

One of the key noise sources that currently limits high-contrast imaging observations for exoplanet detection is quasi-static speckles. Quasi-static speckles originate from slowly evolving non-common path aberrations (NCPA). The purpose of this work is to present a proof-of-concept on-sky demonstration of spatial Linear Dark Field Control (LDFC). The ultimate goal of LDFC is to stabilize the point spread function (PSF) by addressing NCPA using the science image as additional wavefront sensor. We combined spatial LDFC with the Asymmetric Pupil vector-Apodizing Phase Plate (APvAPP) on the Subaru Coronagraphic Extreme Adaptive Optics system at the Subaru Telescope. In this paper, we report the results of the first successful proof-of-principle LDFC on-sky tests. We present results from two types of cases: (1) correction of instrumental errors and atmospheric residuals plus artificially induced static aberrations introduced on the deformable mirror and (2) correction of only atmospheric residuals and instrumental aberrations. When introducing artificial static wavefront aberrations on the DM, we find that LDFC can improve the raw contrast by a factor of $3$--$7$ over the dark hole. In these tests, the residual wavefront error decreased by $\sim$50 nm RMS, from $\sim$90 nm to $\sim 40$ nm RMS. In the case with only residual atmospheric wavefront errors and instrumental aberrations, we show that LDFC is able to suppress evolving aberrations that have timescales of $<0.1$--$0.4$ Hz. We find that the power at $10^{-2}$ Hz is reduced by a factor of $\sim$20, 7, and 4 for spatial frequency bins at 2.5, 5.5, and 8.5 $\lambda /D$, respectively. The results presented in this work show that LDFC is a promising technique for enabling the high-contrast imaging goals of the upcoming generation of extremely large telescopes.

Accepted for publication in Astronomy&Astrophysics. 13 pages, 11 figures, 2 tables

References in corpus (12)

• The NumPy array: a structure for efficient numerical computation
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The Gemini Planet Imager: First Light
• Fundamental limitations of high contrast imaging set by small sample statistics
• Discovery of a warm, dusty giant planet around HIP65426
• On-sky speckle nulling demonstration at small angular separation with SCExAO
• SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
• A New Standard for Assessing the Performance of High Contrast Imaging Systems
• On-sky verification of Fast and Furious focal-plane wavefront sensing: Moving forward toward controlling the island effect at Subaru/SCExAO
• Visible and Near Infrared Laboratory Demonstration of a Simplified Pyramid Wavefront Sensor
• Active minimization of non-common path aberrations in long-exposure imaging of exoplanetary systems
• Laboratory Demonstration of Spatial Linear Dark Field Control For Imaging Extrasolar Planets in Reflected Light