Stellar coronagraph using the principle of achromatic null-interferometer

• Published in: Cosmic research 2011-04, Vol.49 (2), p.99-109
• Main Authors: Tavrov, A. V., Korablev, O. I., Rodin, A. V., Vinogradov, I. I., Trokhimovsky, A. Yu, Ivanov, A. Yu, Ksanfomaliti, L. V., Orlov, D. A.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics and Astroparticles; Astrophysics and Cosmology; Physics; Physics and Astronomy; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics
• ISSN: 0010-9525; 1608-3075
• DOI: 10.1134/S0010952511020109

In order to observe exoplanets we propose a space-based achromatic stellar coronagraph combined with a 0.8–1.5 m telescope. We develop an achromatic common path interferometer for observing an exoplanet (a faint off-axis source) on the background of a hoste star (bright axial source). An image of the star and its copy acquire an achromatic phase shift by 180° and interfere in antiphase. The achromatic phase shift is caused by geometric phase in the scheme of a three-dimensional interferometer. The interference process divides spatially the dark and light fields of the star image redirecting them to the opposite sides of a beam splitter. The interference process does not weaken the image of a planet, with equal intensities it is redirected to both sides of a beam splitter. The suggested scheme of common path interferometer ensures mechanical stability. The background signal is experimentally demonstrated to be reduced by six orders of magnitude.