EAS Publications Series
Volume 8, 2003Astronomy with High Contrast Imaging
|Page(s)||117 - 128|
|Published online||28 May 2003|
Claude Aime and Rémi Soummer (eds)
EAS Publications Series, 8 (2003) 117-128
Achromatic Four Quadrant Phase Mask Coronagraph using the Dispersion of Form Birefringence
IAGL, Université de Liège, 17, B5C
Allée du 6 Août, 4000 Sart Tilman, Belgium
2 HOLOLAB, Université de Liège, 17, B5 Allée du 6 Août, 4000 Sart Tilman, Belgium
3 DESPA, Observatoire de Paris-Meudon, 5 Pl. J. Janssen, 92195 Meudon, France
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 π 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 efficiency is maintained within a wide wavelength range. Numerical simulations were made according to the RCWA (Rigorous Coupled Wave Analyses).
© EAS, EDP Sciences, 2003
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