High-contrast demonstration of a vector vortex coronagraph with a segmented, off-axis aperture

One of the most profound scientific questions is whether there are other Earth-like worlds. To image such exoplanets directly, the Astro2020 Decadal Survey highly recommends technology development for a future 6-meter, space-based observatory equipped with a coronagraph. The vector vortex coronagraph (VVC) is a top candidate for providing the necessary $10^{-10}$ planet-to-star contrast ratio needed at small angular separations to image and characterize Earth-like exoplanets. The VVC is best suited for an unobscured aperture, but for a 6-meter, space-based observatory the primary mirror may need to be segmented. In this paper, we describe our laboratory experiments testing a charge four VVC with a segmented, off-axis entrance pupil. The extra diffraction from the pupil segmentation was suppressed with the single Boston Micromachines deformable mirror in the optical system. We achieved a mean normalized intensity of $4.7\times10^{-9}$ from $3-10$ $\lambda/D$ in a 10\% spectral bandwidth in the Decadal Survey Testbed at the Jet Propulsion Laboratory. To determine our current limitations and to enable $10^{-10}$ contrast in future tests, we compare to other testbed results with a monolithic aperture.