ES-07-0008

2 Fast 2 Furious: Controlling coronagraphic PSF quality for direct imaging

Samuel Walker, Michael Bottom, Laurent Pueyo

We present 2 Fast 2 Furious, an algorithm for focal plane wavefront control using a sequential phase diversity approach with a coronagraph in the optical path. Our algorithm builds on the existing Fast and Furious algorithm, which has been proven to work swiftly in the loop on the bench and on sky to suppress wavefront aberrations and improve PSF quality. We adapt the formalism of Fast and Furious to incorporate a coronagraph focal plane mask and Lyot stop. Our algorithm performs well in the low aberration regime (<1 radian RMS) for focal plane masks with inner working angles ? 2λ/D, reducing the total RMS WFE from 1 radian to <0.1 radians. Additionally, we present data illustrating that our algorithm works in practice on the Keck/NIRC2 lab bench. This is the first sequential phase diversity focal plane wavefront control algorithm shown to work with a focal plane coronagraph, facilitating higher-contrast observations at closer angular separations than previously possible.