10-μm wavefront spatial filtering: first results with chalcogenide fibers

Wavefront cleaning by single-mode fibers has proved to be efficient in optical-infrared interferometry to improve calibration quality. For instance, the FLUOR instrument has demonstrated the capability of fluoride glass single-mode fibers in this respect in the K and L bands. New interferometric instruments developed for the mid-infrared require the same capability for the 8-12 μm range. We have initiated a program to develop single-mode fibers in the prospect of the VLTI mid-infrared instrument MIDI and of the ESA/DARWIN and NASA/TPF missions that require excellent wavefront quality. In order to characterize the performances of chalcogenide fibers we are developing, we have set up an experiment to measure the far-field pattern radiated at 10 μm. In this paper, we report the first and promising results obtained with this new component.