Improved achromatization of phase mask coronagraphs using colored apodization

Abstract

For direct imaging of exoplanets, a stellar coronagraph helps to remove the image of an observed bright star by attenuating the diffraction effects caused by the telescope aperture of diameter D. The Dual Zone Phase Mask (DZPM) coronagraph constitutes a promising concept since it theoretically offers a small inner working angle (IWA \sim λ_0/D), good achromaticity and high starlight rejection, typically reaching a 1e6 contrast at 5 λ_0/D from the star over a spectral bandwidth Δλ/λ_0 of 25% (similar to H-band). This last value proves to be encouraging for broadband imaging of young and warm Jupiter-like planets. Contrast levels higher than 1e6 are however required for the observation of older and/or less massive companions over a finite spectral bandwidth. An achromatization improvement of the DZPM coronagraph is therefore mandatory to reach such performance. In its design, the DZPM coronagraph uses a grey (or achromatic) apodization. We propose to replace it by a colored apodization to increase the performance of this coronagraphic system over a large spectral range. This innovative concept, called Colored Apodizer Phase Mask (CAPM) coronagraph, is defined with some design parameters optimized to reach the best contrast in the exoplanet search area. Once this done, we study the performance of the CAPM coronagraph in the presence of different errors to evaluate the sensitivity of our concept. A 2.5 mag contrast gain is estimated from the performance provided by the CAPM coronagraph with respect to that of the DZPM coronagraph. A 2.2e-8 intensity level at 5 λ_0/D separation is then theoretically achieved with the CAPM coronagraph in the presence of a clear circular aperture and a 25% bandwidth. In addition, our studies show that our concept is less sensitive to low than high-order aberrations for a given value of rms wavefront errors.

20 pages, 26 figures, accepted in A&A

References in corpus (21)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Angular Differential Imaging: a Powerful High-Contrast Imaging Technique
• A giant planet imaged in the disk of the young star Beta Pictoris
• Optical Images of an Exosolar Planet 25 Light Years from Earth
• A new algorithm for point spread function subtraction in high-contrast imaging: a demonstration with angular differential imaging
• Theoretical Limits on Extrasolar Terrestrial Planet Detection with Coronagraphs
• Imaging Spectroscopy for Extrasolar Planet Detection
• Apodized Pupil Lyot Coronagraphs for Arbitrary Telescope Apertures
• Phase-Induced Amplitude Apodization of Telescope Pupils for Extrasolar Terrestrial Planet Imaging
• A Coronagraph with a Band-Limited Mask for Finding Terrestrial Planets
• Fast computation of Lyot-style coronagraph propagation
• Exoplanets imaging with a Phase-Induced Amplitude Apodization Coronagraph - I. Principle
• A New High Contrast Imaging Program at Palomar Observatory
• High-Contrast Observations in Optical and Infrared Astronomy
• Exoplanet characterization with long slit spectroscopy
• Eighth-Order Image Masks for Terrestrial Planet Finding
• An Eight-Octant Phase-Mask Coronagraph
• On-Line Long-Exposure Phase Diversity: a Powerful Tool for Sensing Quasi-Static Aberrations of Extreme Adaptive Optics Imaging Systems
• Comparison of coronagraphs for high contrast imaging in the context of Extremely Large Telescopes
• Low Order Aberrations in Band-Limited Lyot Coronagraphs
• Diffraction-Based Sensitivity Analysis of Apodized Pupil Mapping Systems

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• Laboratory validation of the dual-zone phase mask coronagraph in broadband light at the high-contrast imaging THD-testbed
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