28 June 2006 Development of broadband infrared single-mode fibers for the DARWIN mission
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A vital function of the space interferometer foreseen in the DARWIN mission is the so-called "nulling" operation. The challenge of nulling is making the null in the interferometric signal sufficiently deep to cancel the light from the bright star during the collection of light from its surrounding planets. The performance of the nulling is limited by the wavefront quality of the beams. The wavefront error can be reduced by filtering. One promising concept for nulling wavefront filtering is using a single mode fiber. For the wavefront filtering in the DARWIN mission, the fiber has to cover the operational wavelength range of 4-20 μm. Furthermore, a minimal insertion loss is required to ensure a minimum exposure time. This results in the separation of the complete wavelength range into several separate wavelength bands in the nulling system. Within an ESA project, a chalcogenide glass fiber based on the Te-As-Se (TAS) composition is selected to be used for the short wavelength band. TNO has designed and tested several TAS fibers that have been manufactured by the University of Rennes. Single mode operation is demonstrated. Furthermore, the effect of bending the fiber and light coupling are investigated. For the long wavelength band up to 20 μm, Tellurium based glass is proposed. Different samples of various composition based on Te glass are manufactured. Accurate temperature control to avoid crystallization is found to be essential for the manufacturing process. For the bulk material, a transmission window up to 20 μm is measured.
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Lun K. Cheng, Lun K. Cheng, Anne-Jans Faber, Anne-Jans Faber, Wim Gielesen, Wim Gielesen, Jacques Lucas, Jacques Lucas, Catherine Boussard-Plédel, Catherine Boussard-Plédel, Patrick Houizot, Patrick Houizot, João Pereira do Carmo, João Pereira do Carmo, } "Development of broadband infrared single-mode fibers for the DARWIN mission", Proc. SPIE 6268, Advances in Stellar Interferometry, 62682F (28 June 2006); doi: 10.1117/12.671500; https://doi.org/10.1117/12.671500


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