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 μm precision using an electron-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 .