Comparing focal plane wavefront control techniques:\\Numerical simulations and laboratory experiments

Abstract

Fewer than 1% of all exoplanets detected to date have been characterized on the basis of spectroscopic observations of their atmosphere. Unlike indirect methods, high-contrast imaging offers access to atmospheric signatures by separating the light of a faint off-axis source from that of its parent star. Forthcoming space facilities, such as WFIRST/LUVOIR/HabEX, are expected to use coronagraphic instruments capable of imaging and spectroscopy in order to understand the physical properties of remote worlds. The primary technological challenge that drives the design of these instruments involves the precision control of wavefront phase and amplitude errors. Several FPWS and control techniques have been proposed and demonstrated in laboratory to achieve the required accuracy. However, these techniques have never been tested and compared under the same laboratory conditions. This paper compares two of these techniques in a closed loop in visible light: the pair-wise (PW) associated with electric field conjugation (EFC) and self-coherent camera (SCC). We first ran numerical simulations to optimize PW wavefront sensing and to predict the performance of a coronagraphic instrument with PW associated to EFC wavefront control, assuming modeling errors for both PW and EFC. Then we implemented the techniques on a laboratory testbed. We introduced known aberrations into the system and compared the wavefront sensing using both PW and SCC. The speckle intensity in the coronagraphic image was then minimized using PW+EFC and SCC independently. We demonstrate that both SCC and PW+EFC can generate a dark hole in space-like conditions in a few iterations. Both techniques reach the current limitation of our laboratory bench and provide coronagraphic contrast levels of 5e-9 in a narrow spectral band (<0.25% bandwidth)

12 pages, 11 figures. Accepted for publication in section 13. Astronomical instrumentation of A&A

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Cited by in corpus (12)

• Implicit electric field Conjugation: Data-driven focal plane control
• Imaging exoplanets with coronagraphic instruments
• Increasing the raw contrast of VLT/SPHERE with the dark hole technique. I. Simulations and validation on the internal source
• Increasing the raw contrast of VLT/SPHERE with the dark-hole technique. II. On-sky wavefront correction and coherent differential imaging
• Millisecond Exoplanet Imaging, I: Method and Simulation Results
• Wavefront tolerances of space-based segmented telescopes at very high contrast: Experimental validation
• The polarization-encoded self-coherent camera
• High Speed Focal Plane Wavefront Sensing with an Optical Chopper
• Modeling and performance analysis of Implicit Electric Field Conjugation with two deformable mirrors applied to the Roman Coronagraph
• Comparative laboratory study of electric field conjugation algorithms
• Extended Linearity in the High-Order Wavefront Sensor for the Roman Coronagraph
• Low-order wavefront control using a Zernike sensor through Lyot coronagraphs for exoplanet imaging