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Astrophysics Colloquium

Recent Progress in Achromatic Photonic-Crystal Coronagraph Masks
Presented by Noashi Murakami and Jun Nishikawa
Hokkaido University and National Astronomical Observatory, respectively, Japan

Monday, March 23, 2015
12:00 noon in 169-336

Abstract
A photonic crystal is an artificial periodic nanostructure of high and low refractive indices. Various coronagraph masks have been manufactured based on photonic-crystal technology, including an eight-octant phase mask (8OPM), and 2nd-order and 4th-order vector vortex masks. In this presentation, I report our recent progress in achievable contrast with a three-layer super-achromatic 8OPM, the development of a polarimetric mode, and a fore-optics system for reducing the effect of a central obscuration due to a secondary mirror, which we call the CRP (central-obscuration removal plates). In the latter part of the presentation, Jun Nishikawa will present our recent activities of wavefront measurement and correction scheme based on the UNI-PAC (unbalanced nulling interferometory and phase-amplitude correction) method.

About the Speaker
Naoshi Murakami is an Assistant Professor in the Division of Applied Physics, Faculty of Engineering, Hokkaido University, Sapporo, Japan. He was also a visitor at JPL for most of 2013.

Jun Nishikawa is at the NAOJ, and is also a frequent visitor to JPL.


SVCP Astrophysics


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