Towards 10¹⁰ Contrast for NASA's Terrestrial Planet Finder Mission: Demonstration of High Contrast in a Shaped-Pupil Coronagraph at Princeton

Abstract

Our group at Princeton University is developing the Shaped-Pupil Coronagraph (SPC) as a solution to the high contrast imaging requirements for NASA's Terrestrial Planet Finder mission. At the heart of the SPC is a specially designed shaped mask at the pupil plane, and a star occulter at the image plane. We report a measurement of $10^{5}$ contrast at 4 $\lambda/D$ and $10^{6}$ at 7 $\lambda/D$, with no adaptive optics corrections. This contrast is maintained at laser wavelengths of 532, 594, and 632nm, and for broadband light from at least 550nm to 750nm. The contrast is almost certainly limited by wavefront aberrations in the mirrors. Indeed, the level and general structure of the speckles in the high contrast region is consistent with statistical simulations of our optics.