Spatial linear dark field control: stabilizing deep contrast for exoplanet imaging using bright speckles

Kelsey Miller,Jared Males,Olivier Guyon

doi:10.1117/1.jatis.3.4.049002

Abstract

Direct imaging of exoplanets requires establishing and maintaining a high-contrast dark field (DF) within the science image to a high degree of precision (10−10). Current approaches aimed at establishing the DF, such as electric field conjugation (EFC), have been demonstrated in the lab and have proven capable of high-contrast DF generation. The same approaches have been considered for the maintenance of the DF as well. However, these methods rely on phase diversity measurements, which require field modulation; this interrupts the DF and consequently competes with the science acquisition. We introduce and demonstrate spatial linear dark field control (LDFC) as an alternative technique by which the high-contrast DF can be maintained without modulation. Once the DF has been established by conventional EFC, spatial LDFC locks the high-contrast state of the DF by operating a closed loop around the linear response of the bright field (BF) to wavefront variations that modify both the BF and the DF. We describe the fundamental operating principles of spatial LDFC and provide numerical simulations of its operation as a DF stabilization technique that is capable of wavefront correction within the DF without interrupting science acquisition.

Highlights

In the last two decades, the existence of 3,498 exoplanets has been confirmed,[1] and in the upcoming era of 30-m class groundbased telescopes and new space-based observatories, there is the promise of discovery, even characterization, of many more exoplanets, including potentially Earth-like worlds
To demonstrate spatial linear dark field control (LDFC)’s ability to maintain the high-contrast dark field (DF), a 6.5-m telescope system was constructed in simulation, which included a single deformable mirror (DM) and Lyot coronagraph that removed approximately two orders of magnitudes of stellar light from the final image
We have demonstrated here that spatial LDFC is capable of locking the DF contrast at its ideal electric field conjugation (EFC) state using only the bright field (BF) response to a perturbation in the optical path

Summary

Introduction

In the last two decades, the existence of 3,498 exoplanets has been confirmed,[1] and in the upcoming era of 30-m class groundbased telescopes and new space-based observatories, there is the promise of discovery, even characterization, of many more exoplanets, including potentially Earth-like worlds. With such powerful capabilities on the horizon, it has become imperative to push stellar suppression technology to higher precision in order to directly image these exoplanets. Current speckle nulling techniques[2] are capable of creating the dark field (DF) in the science image where light from an exoplanet orbiting its star can be detected. For high-contrast imaging, the WFS should ideally be common path with all of the optics seen by the science

Results

Discussion

Conclusion