High-contrast imaging in polychromatic light with the self-coherent camera

Abstract

Context. In the context of direct imaging of exoplanets, coronagraphs are commonly proposed to reach the required very high contrast levels. However, wavefront aberrations induce speckles in their focal plane and limit their performance. Aims. An active correction of these wavefront aberrations using a deformable mirror upstream of the coronagraph is mandatory. These aberrations need to be calibrated and focal-plane wavefront-sensing techniques in the science channel are being developed. One of these, the self-coherent camera, of which we present the latest laboratory results. Methods. We present here an enhancement of the method: we directly minimized the complex amplitude of the speckle field in the focal plane. Laboratory tests using a four-quadrant phase-mask coronagraph and a 32x32 actuator deformable mirror were conducted in monochromatic light and in polychromatic light for different bandwidths. Results. We obtain contrast levels in the focal plane in monochromatic light better than 3.10^-8 (RMS) in the 5 - 12 λ/D region for a correction of both phase and amplitude aberrations. In narrow bands (10 nm) the contrast level is 4.10^-8 (RMS) in the same region. Conclusions. The contrast level is currently limited by the amplitude aberrations on the bench. We identified several improvements that can be implemented to enhance the performance of our optical bench in monochromatic as well as in polychromatic light.

4 pages, 3 figures, accepted in Astronomy & Astrophysics (02/2014)

References in corpus (3)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Estimation and correction of wavefront aberrations using the self-coherent camera: laboratory results
• Improved achromatization of phase mask coronagraphs using colored apodization

Cited by in corpus (20)

• Recursive Starlight and Bias Estimation for High-Contrast Imaging with an Extended Kalman Filter
• Active correction of aperture discontinuities - optimized stroke minimization II: optimization for future missions
• Focal plane wavefront sensor achromatization : The multireference self-coherent camera
• Comparing focal plane wavefront control techniques:\\Numerical simulations and laboratory experiments
• A Family of Phase Masks For Broadband Coronagraphy Example of the Wrapped Vortex Phase Mask Theory and Laboratory demonstration
• Active correction of aperture discontinuities - optimized stroke minimization I: a new adaptive interaction matrix algorithm
• Review of high-contrast imaging systems for current and future ground- and space-based telescopes I. Coronagraph design methods and optical performance metrics
• Fast Coherent Differential Imaging on Ground-Based Telescopes using the Self-Coherent Camera
• Active minimization of non-common path aberrations in long-exposure imaging of exoplanetary systems
• Active compensation of aperture discontinuities for WFIRST-AFTA: analytical and numerical comparison of propagation methods and preliminary results with a WFIRST-AFTA-like pupil
• Active correction of aperture discontinuities (ACAD) for space telescope pupils: a parametic analysis
• Minimization of non common path aberrations at the Palomar telescope using a self-coherent camera
• The spectrally modulated self-coherent camera (SM-SCC): Increasing throughput for focal-plane wavefront sensing
• The polarization-encoded self-coherent camera
• Demonstration of broadband contrast at 1.2 $\lambda$/D and greater for the EXCEDE Starlight Suppression System
• Fundamental limits to high-contrast wavefront control
• Capabilities of ACAD-OSM, an active method for the correction of aperture discontinuities
• High contrast imaging of exoplanets on ELTs using a super-Nyquist wavefront control scheme
• Extended Linearity in the High-Order Wavefront Sensor for the Roman Coronagraph
• Correcting for the effects of pupil discontinuities with the ACAD method