Achromatic eight-octant phase-mask coronagraph using photonic crystal

Abstract

We designed and manufactured a photonic-crystal mask which can be used for an achromatic eight-octant phase-mask (EOPM) coronagraph for direct detection of extrasolar planets. Laboratory experiments of the EOPM coronagraph were carried out using two laser light sources as a simulated star (wavelengths of 532 and 633nm). As a result, we attained high extinction of the simulated starlight in both the wavelengths. Halo intensity levels of about 10-6 and 10 -7 were achieved at an angular distance of 3 and 13λ/D, respectively. We also discuss several issues, such as an effect of phase aberration on the coronagraphic performance, a transmittance of the proposed EOPM, and a novel two-channel coronagraphic configuration to improve system throughput. © 2010. The American Astronomical Society. All rights reserved.