Astronomers have partially solved the problem of looking at objects near to a star's bright glare by inventing the coronagraph, which focuses all the incoming light around a dark spot in the telescope's innards, neatly clipping off most of the central starlight and passing on much of the planetary glow. For exoplanet hunting that is not quite good enough. Some of the starlight still gets through, easily obscuring planets that are millions of times fainter than their parent stars.
A novel approach plays with the peaks and troughs of the light waves to do the job more effectively. This week, in Nature, Eugene Serabyn of the Jet Propulsion Laboratory in California and his colleagues describe a stunning implementation of an optical vortex coronagraph. In place of a dark spot, this uses a disk of glassy material, etched with a carefully designed pattern which changes the phase of the incoming light, in effect twisting it back onto itself and creating a dark hole in the center of the image.
Serabyn has contributed 60 papers to SPIE conferences over the past two decades. He is an author or coauthor of several scheduled for the SPIE Astronomical Instrumentation symposium in San Diego, 27 June to 2 July 2010.
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