High‐Contrast Imaging with Gaussian Aperture Pupil Masks

Gaussian aperture pupil masks (GAPMs) can, in theory, achieve the requisite contrast for directly imaging an extrasolar planet around a nearby solar‐type star. We outline the process of designing, fabricating, and testing a GAPM for use on current telescopes, and specifically the Penn State near‐IR Imager and Spectrograph (PIRIS) at the Mount Wilson 100 inch (2.54 m) telescope. We find that the initial prototype observations are quite successful, achieving a contrast similar to a traditional Lyot coronagraph without blocking any light from a central object, and useful for finding faint companions to nearby young solar analogues. In the lab, we can reproduce the expected point‐spread function reasonably well and with a single‐aperture design that achieves ∼ 4 × 10-5 contrast at 10 λ/D. We find that small inaccuracies in the mask fabrication process and insufficient correction of the atmosphere contribute the most degradation to contrast at these levels.