Using notch filter masks for high-contrast imaging of extra solar 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 notchfilter mask prototype with .25 µm precision using an e-beam lithography machine. Our initial optical tests show that the prototype masks generate contrast levels of 10 −5 at 3λ/D and 10 −6 at ∼ 8λ/D, with a throughput of 27%. We speculate on the "as-is" performance of such a mask in the Hubble Space Telescope.