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A diamond AGPM coronagraph for VISIR

Delacroix, C. and Absil, O. and Mawet, D. and Hanot, C. and Karlsson, M. and Forsberg, P. and Pantin, E. and Surdej, J. and Habraken, S. (2012) A diamond AGPM coronagraph for VISIR. In: Ground-based and Airborne Instrumentation for Astronomy IV. Proceedings of SPIE. No.8446. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 84468K . ISBN 9780819491473. https://resolver.caltech.edu/CaltechAUTHORS:20150521-133310682

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Abstract

In recent years, phase mask coronagraphy has become increasingly efficient in imaging the close environment of stars, enabling the search for exoplanets and circumstellar disks. Coronagraphs are ideally suited instruments, characterized by high dynamic range imaging capabilities, while preserving a small inner working angle. The AGPM (Annular Groove Phase Mask, Mawet et al. 2005) consists of a vector vortex induced by a rotationally symmetric subwavelength grating. This technique constitutes an almost unique solution to the achromatization at longer wavelengths (mid-infrared). For this reason, we have specially conceived a mid-infrared AGPM coronagraph for the forthcoming upgrade of VISIR, the mid-IR imager and spectrograph on the VLT at ESO (Paranal), in collaboration with members of the VISIR consortium. The implementation phase of the VISIR Upgrade Project is foreseen for May-August 2012, and the AGPM installed will cover the 11-13.2 μm spectral range. In this paper, we present the entire fabrication process of our AGPM imprinted on a diamond substrate. Diamond is an ideal material for mid-infrared wavelengths owing to its high transparency, small dispersion, extremely low thermal expansion and outstanding mechanical and chemical properties. The design process has been performed with an algorithm based on the rigorous coupled wave analysis (RCWA), and the micro-fabrication has been carried out using nano-imprint lithography and reactive ion etching. A precise grating profile metrology has also been conducted using cleaving techniques. Finally, we show the deposit of fiducials (i.e. centering marks) with Aerosol Jet Printing (AJP). We conclude with the ultimate coronagraph expected performances.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1117/12.926494DOIArticle
http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1362627PublisherArticle
ORCID:
AuthorORCID
Absil, O.0000-0002-4006-6237
Mawet, D.0000-0002-8895-4735
Karlsson, M.0000-0002-2011-0851
Surdej, J.0000-0002-7005-1976
Additional Information:© 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). Paper Date Published: 24 September 2012. C. Delacroix gratefully acknowledges the financial support of the Belgian Fonds pour la formation à la Recherche dans l'Industrie et dans l'Agriculture (FRIA) and Fonds de solidarité ULg. The authors from the Liège University acknowledge support from the Communauté française de Belgique - Actions de recherche concertée - Académie universitaire Wallonie-Europe.
Funders:
Funding AgencyGrant Number
Belgian Fonds pour la formation à la Recherche dans l'Industrie et dans l'Agriculture (FRIA) and Fonds de solidarité ULgUNSPECIFIED
Communauté française de Belgique - Actions de recherche concertée - Académie universitaire Wallonie-EuropeUNSPECIFIED
Subject Keywords:coronagraphy, phase mask, high dynamic range, achromatization, subwavelength grating, vector vortex, exoplanet, circumstellar matter
Series Name:Proceedings of SPIE
Issue or Number:8446
Record Number:CaltechAUTHORS:20150521-133310682
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150521-133310682
Official Citation:C. Delacroix ; O. Absil ; D. Mawet ; C. Hanot ; M. Karlsson, et al. " A diamond AGPM coronagraph for VISIR ", Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84468K (September 24, 2012); doi:10.1117/12.926494; http://dx.doi.org/10.1117/12.926494
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57745
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:21 May 2015 22:31
Last Modified:03 Oct 2019 08:28

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