We describe an alternative design for the 4-quadrant phase mask coronagraph described recently by Rouan et al. 2000. Based on the same principle, i.e. producing a very efficient nulling by mutually destructive interferences of the coherent light from the main source, our mask realises the pi phase shift using some properties of ZOGs (Zeroth Order Gratings) and according to an original scheme respecting the 4-quadrant symmetry. When the period of the one-dimension grating structure is smaller than the wavelength of the incident light, the structure becomes birefringent. The effective refractive indices depend on the wavelength. Using this feature, we can design a mask whose nulling e±ciency is maintained within a wide wavelength range. Numerical simulations were made according to the RCWT (Rigorous Coupled Wave Theory).

Date Published: 3 March 2003
PDF: 10 pages
Proc. SPIE 4860, High-Contrast Imaging for Exo-Planet Detection, (3 March 2003); doi: 10.1117/12.457918

Published in SPIE Proceedings Vol. 4860:
High-Contrast Imaging for Exo-Planet Detection
Alfred B. Schultz; Richard G. Lyon, Editor(s)