title: Cascade six-level phase-mask achromatic coronagraph.
abstract: A cascade six-level phase-mask achromatic coronagraph is proposed. We show that, for the ideal aberration-free case, the average suppression of the central starlight in a three-stage six-level phase-mask achromatic coronagraph (SLPMC) can reach about 10⁻⁸ over a 40% bandwidth. We also do the optimization analysis of the working wavelength of each phase mask in the three-stage SLPMC. With optimization, the starlight can be stably suppressed to less than 10⁻⁸ (average about 10⁻¹⁰) over the whole 40% bandwidth.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Ge
authors.forename: Qing
authors.initials: Q
authors.lastname: Cao
authors.forename: Rongfei
authors.initials: R
authors.lastname: Hu
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Xiegang
authors.initials: X
authors.lastname: Tong