Using Notch-Filter Masks for High Contrast Imaging of Extrasolar Planets

Abstract

We present the first laboratory experiments using a notch-filter mask, a coronagraphic image mask that can produce infinite dynamic range in an ideal Lyot coronagraph according to scalar diffraction theory. We fabricated the first notch-filter mask prototype with .25 $\micron$ precision using an e-beam lithography machine. Our initial optical tests show that the prototype masks generate contrast levels of 10$^{-5}$ at 3$\lambda/D$ and 10$^{-6}$ at $\sim 8\lambda/D$, with a throughput of 27%. We speculate on the ``as-is'' performance of such a mask in the Hubble Space Telescope.