Vector vortex coronagraph: first results in the visible

Abstract

We report the status of JPL and JDSU ongoing technological developments and contrast results of the vector vortex coronagraph (VVC) made out of liquid crystal polymers (LCP). The first topological charge 4 VVC was tested on the high contrast imaging testbed (HCIT) around 800 nm, under vacuum and with active wavefront control (32x32 Xinetics deformable mirror). We measured the inner working angle or IWA (50% off-axis transmission) at ~ 1.8λ/d. A one-sided dark hole ranging from 3λ/d to 10λ/d was created in polarized light, showing a mean contrast of ~ 2 × 10^-7 over a 10% bandwidth. This contrast was maintained very close in (3 λ/d) in a reduced 2% bandwidth. These tests begin to demonstrate the potential of the LCP technology in the most demanding application of a space-based telescope dedicated to extrasolar planet characterization. The main limitations were identified as coming from incoherent sources such as multiple reflections, and residual chromaticity. A second generation of improved masks tackling these issues is being manufactured and will be tested on the HCIT in the coming months.