We discuss the use of parametric phase-diverse phase retrieval to characterize and optimize the transmitted wavefront of a high-contrast apodized pupil coronagraph with and without an apodizer. We apply our method to correct the transmitted wavefront of the HiCAT (High contrast imager for Complex Aperture Telescopes) coronagraphic testbed. This correction requires a series of calibration steps, which we describe. The correction improves the system wavefront from 16 nm RMS to 3.0 nm RMS for the case where a uniform circular aperture is in place. We further measure the wavefront with the apodizer in place to be 11.7 nm RMS. Improvement to the apodized pupil phase retrieval process is necessary before a correction based on this measurement can be applied.

Date Published: 9 September 2019
PDF: 17 pages
Proc. SPIE 11117, Techniques and Instrumentation for Detection of Exoplanets IX, 1111712 (9 September 2019); doi: 10.1117/12.2530482

Published in SPIE Proceedings Vol. 11117:
Techniques and Instrumentation for Detection of Exoplanets IX
Stuart B. Shaklan, Editor(s)