Using notch-filter masks for high-contrast imaging of extrasolar planets

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 0.25 mum precision using an electron-beam lithography machine. Our initial optical tests show that the prototype masks generate contrast levels of 10(-5) at 3lambda/D and 10(-6) at similar to8lambda/D, with a throughput of 27%. We speculate on the "as-is" perfomance of such a mask in the Hubble Space Telescope.