Multi-stage four-quadrant phase mask: achromatic coronagraph for space-based and ground-based telescopes
Abstract
Context. Less than 3% of the known exoplanets were directly imaged for two main reasons. They are angularly very close to their parent star, which is several magnitudes brighter. Direct imaging of exoplanets thus requires a dedicated instrumentation with large telescopes and accurate wavefront control devices for high-angular resolution and coronagraphs for attenuating the stellar light. Coronagraphs are usually chromatic and they cannot perform high-contrast imaging over a wide spectral bandwidth. That chromaticity will be critical for future instruments.
Aims: Enlarging the coronagraph spectral range is a challenge for future exoplanet imaging instruments on both space- and ground-based telescopes.
Methods: We propose the multi-stage four-quadrant phase mask that associates several monochromatic four-quadrant phase mask coronagraphs in series. Monochromatic device performance has already been demonstrated and the manufacturing procedures are well-under control since their development for previous instruments on VLT and JWST. The multi-stage implementation simplicity is thus appealing.
Results: We present the instrument principle and we describe the laboratory performance for large spectral bandwidths and for both pupil shapes for space- (off-axis telescope) and ground-based (E-ELT) telescopes.
Conclusions: The multi-stage four-quadrant phase mask reduces the stellar flux over a wide spectral range and it is a very good candidate to be associated with a spectrometer for future exoplanet imaging instruments in ground- and space-based observatories.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- June 2011
- DOI:
- 10.1051/0004-6361/201116675
- arXiv:
- arXiv:1104.2903
- Bibcode:
- 2011A&A...530A..43G
- Keywords:
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- instrumentation: high angular resolution;
- techniques: high angular resolution;
- methods: laboratory;
- methods: numerical;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 7 pages, 11 figures, 4 tables, accepted in A&