A high-contrast coronagraph for direct imaging of Earth-like exoplanets: design and test^*

A high-contrast coronagraph for direct imaging of an Earth-like exoplanet at the visible band needs a contrast of 10⁻¹⁰ at a small angular separation of 4λ/D or less. Here we report our recent laboratory experiment that approaches these limits. Our test of a high-contrast imaging coronagraph is based on our step-transmission apodized filter. To achieve this goal, we use a liquid crystal array as a phase corrector to create a dark hole based on our dedicated algorithm. We have suppressed the diffraction and speckle noise near the point image of a star to a level of 1.68 × 10⁻⁹ at 4λ/D, which can be used for direct imaging of Jupiter-like exoplanets. This demonstrates that a telescope incorporating a high-contrast coronagraph in space has the potential to detect and characterize Earth-like planets.