Integrated optics, applied to astronomical interferometry, bring several decisive benefits compared to bulk optics : mechanical and thermal stability, small size, facility to realize combiners for many telescopes. At this time, numerous compoments were dezigned, realized and tested for stellar interferometry applications. Laboratory characterization in the VIS/NIR wavelengths confirm the expected capabilities and performances.
At thermal infrared wavelengths, the concept of integrated optics is of great interest for spatial instrumentations and particulary for the Darwin/IRSI mission. The aim of the mission, launched in 2012−2015, is the detection and the spectroscopic study of extrasolar planets. Our long term goal is the development of monomode integrated optic components for thermal infrared wavelengths. In the near futur, we are interested by the conception and the realization of single mode straight waveguide for using in modal filtering.
In this paper, we present the conception of first thermal waveguide and their characterizations. Around different solutions, we focused our attention on the utilization of chalcogenide glasses because of its wide transmission window, from 1 to 20 microns depending of the material composition, and of the potentially low propagation losses.
We report here the first visibility and closure-phase measurements done with the IONIC instrument at the IOTA interferometer. The IONIC
instrument is presented and preliminary analysis of the results
discussed. Future improvements of IONIC are envisioned.
Emmanuel Laurent, Pierre Kern, Isabelle Schanen, V. Balan, C. Vigreux, Annie Pradel, S. Setzu, P. Ferrand, Robert Romestain, Karine Rousselet-Perraut, Pierre Benech
Spatial filtering is a critical issue to achieve nulling interferometry in the framework of spatial missions aimed at the detection of exoplanets. Several working interferometric instruments take benefit of guided optics for spatial filtering in the near infrared wavelengths and thus provide accurate visibility measurements. Furthermore planar optics would also provide beam combining functions within a single compact and stable device.
Existing telecom technology allows beam combiner manufacturing for
0.8-1.8 micrometers wavelengths. Adaptation of these technologies
is required to cover the scientific domain of ground based interferometry in each atmospheric spectral band and of the spatial missions like IRSI/DARWIN and TPF dedicated to thermal infrared
wavelengths [4-20 micrometers]. We present here some of the most promising materials and their associated technologies for the thermal infrared range. For each of these solutions, based on chalcogenide glasses, semiconductor materials and hollow waveguides, we present some manufactured components with their optical characterizations. We also present a method and test-benches to measure the single-mode wavelength range of waveguides.
Integrated optics in astronomical interferometry at IR wavelength is potentially very attractive compared to bulk optics in particular in the framework of thermal IR interferometric spatial missions aimed at the detection of terrestrial exoplanets like the IRSI/DARWIN mission. It would provide the spatial filtering function together with the beam combining functions inside a compact and stable device.
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