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A Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency

Piron, P. and Delacroix, C. and Huby, E. and Mawet, D. and Karlsson, M. and Ruane, G. and Habraken, S. and Absil, O. and Surdej, J. (2015) A Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency. In: Techniques and Instrumentation for Detection of Exoplanets VII. Proceedings of SPIE. No.9605. Society of Photo-Optical Instrumentation Engineers , Bellingham, WA, Art. No. 96051J. ISBN 978-1-62841-771-5.

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The Annular Groove Phase Mask (AGPM) is a vectorial vortex phase mask. It acts as a half-wave plate with a radial fast axis orientation operating in the mid infrared domain. When placed at the focus of a telescope element provides a continuous helical phase ramp for an on axis sources, which creates the orbital angular momentum. Thanks to that phase, the intensity of the central source is canceled by a down-stream pupil stop, while the off axis sources are not affected. However due to experimental conditions the nulling is hardly perfect. To improve the null, a Mach-Zehnder interferometer containing Dove prisms differently oriented can be proposed to sort out light based on its orbital angular momentum (OAM). Thanks to the differential rotation of the beam, a π phase shift is achieved for the on axis light affected by a non zero OAM. Therefore the contrast between the star and its faint companion is enhanced. Nevertheless, due the Dove prisms birefringence, the performance of the interferometer is relatively poor. To solve this problem, we propose to add a birefringent wave-plate in each arm to compensate this birefringence. In this paper, we will develop the mathematical model of the wave front using the Jones formalism. The performance of the interferometer is at first computed for the simple version without the birefringent plate. Then the effect of the birefringent plate is be mathematically described and the performance is re-computed.

Item Type:Book Section
Related URLs:
URLURL TypeDescription Paper
Mawet, D.0000-0002-8895-4735
Karlsson, M.0000-0002-2011-0851
Ruane, G.0000-0003-4769-1665
Absil, O.0000-0002-4006-6237
Surdej, J.0000-0002-7005-1976
Additional Information:© 2015 SPIE. This work and the author are funded thanks to a European Research Council funding under the European Union’s Seventh Framework Program (ERC Grant Agreement n◦337569).
Funding AgencyGrant Number
European Research Council (ERC)337569
Subject Keywords:Orbital angular momentum, Coronagraphy, Interferometry, Birefringence, Polarization
Series Name:Proceedings of SPIE
Issue or Number:9605
Record Number:CaltechAUTHORS:20160105-070458470
Persistent URL:
Official Citation:P. Piron ; C. Delacroix ; E. Huby ; D. Mawet ; M. Karlsson ; G. Ruane ; S. Habraken ; O. Absil and J. Surdej " A Mach-Zehnder interferometer based on orbital angular momentum for improved vortex coronagraph efficiency ", Proc. SPIE 9605, Techniques and Instrumentation for Detection of Exoplanets VII, 96051J (September 11, 2015); doi:10.1117/12.2189329;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63364
Deposited On:05 Jan 2016 20:58
Last Modified:10 Nov 2021 23:15

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