We present numerical simulations and laboratory experiments on an eight-octant phase-mask (EOPM) coronagraph. The numerical simulations suggest that an achievable contrast for the EOPM coronagraph can be greatly improved as compared to that of a four-quadrant phase-mask (FQPM) coronagraph for a partially resolved star. On-sky transmission maps reveal that the EOPM coronagraph has relatively high optical throughput, a small inner working angle and large discovery space. We have manufactured an eight-segment phase mask utilizing a nematic liquid-crystal device, which can be easily switched between the FQPM and the EOPM modes. The laboratory experiments demonstrate that the EOPM coronagraph has a better tolerance of the tip-tilt error than the FQPM one. We also discuss feasibility of a fully achromatic and high-throughput EOPM coronagraph utilizing a polarization interferometric technique.
@article{arxiv.0809.1510,
title = {An Eight-Octant Phase-Mask Coronagraph},
author = {N. Murakami and R. Uemura and N. Baba and J. Nishikawa and M. Tamura and N. Hashimoto and L. Abe},
journal= {arXiv preprint arXiv:0809.1510},
year = {2009}
}
Comments
17 pages, 6 figures, Accepted for publication in PASP