High-Contrast Coronagraphy

TL;DR

This review discusses the principles, technological developments, and optimization strategies for high-contrast coronagraphs essential for imaging terrestrial exoplanets with ground-based and space telescopes.

Contribution

It provides a comprehensive overview of coronagraph design, wavefront control, and recent technological advances for high-contrast imaging of exoplanets.

Findings

Ground-based telescopes can achieve contrasts of 10^-7 for habitable zone imaging.

Space telescopes can reach contrasts of 10^-10 for solar-type stars.

Active wavefront control and polarization mitigation are crucial for high sensitivity.

Abstract

Imaging terrestrial exoplanets around nearby stars is a formidable technical challenge, requiring the development of coronagraphs to suppress the stellar halo of diffracted light at the location of the planet. In this review, we derive the science requirement for high-contrast imaging, present an overview of diffraction theory and the Lyot coronagraph, and define the parameters used in our optimization. We detail the working principles of coronagraphs both in the laboratory and on-sky with current high-contrast instruments, and we describe the required algorithms and processes necessary for terrestrial planet imaging with the extremely large telescopes and proposed space telescope missions: * Imaging terrestrial planets around nearby stars is possible with a combination of coronagraphs and active wavefront control using feedback from wavefront sensors. * Ground based 8-40m class telescopes can target the habitable zone around nearby M dwarf stars with contrasts of $10^{-7}$ and space telescopes can search around solar-type stars with contrasts of $10^{-10}$. * Focal plane wavefront sensing, hybrid coronagraph designs and multiple closed loops providing active correction are required to reach the highest sensitivities. * Polarization effects need to be mitigated for reaching $10^{-10}$ contrasts whilst keeping exoplanet yields as high as possible. * Recent technological developments, including photonics and microwave kinetic inductance detectors, will be folded into high-contrast instruments.