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Hexabundles: imaging fiber arrays for low-light as
Hexabundles: imaging fiber arrays for low-light astronomical applications
2011
Joss Bland-Hawthorn;Julia Bryant;Gordon Robertson;Peter Gillingham;John O'Byrne;Gerald Cecil;Roger Haynes;Scott Croom;Simon Ellis;Martin Maack;Peter Skovgaard;Danny Noordegraaf
We demonstrate a novel imaging fiber bundle ({dq}hexabundle{dq}) that is suitable for low-light applications in astronomy. The most successful survey instruments at optical-infrared wavelengths use hundreds to thousands of multimode fibers fed to one or more spectrographs. Since most celestial sources are spatially extended on the celestial sphere, a hexabundle provides spectroscopic information at many distinct locations across the source. We discuss two varieties of hexabundles: (i) lightly fused, closely packed, circular cores; (ii) heavily fused non-circular cores with higher fill fractions. In both cases, we find the important result that the cladding can be reduced to {~}2 mum over the short fuse length, well below the conventional {~}10lambda thickness employed more generally, with a consequent gain in fill factor. Over the coming decade, it is to be expected that fiber-based instruments will be upgraded with hexabundles in order to increase the spatial multiplex capability by two or more orders of magnitude.
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