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Modal Filtering for Nulling Interferometry-First Single-Mode Conductive Waveguides in the Mid-Infrared

L. Labadie·P. Labeye·P. Kern·I. Schanen·B. Arezki·J. -E. Broquin
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Abstract

This paper presents the work achieved for the manufacturing and characterization of first single-mode waveguides to be used as modal filters for nulling interferometry in the mid-infrared range [4-20 um]. As very high dynamic range is mandatory for detection of Earth-like planets, modal filtering is one of the most stringent instrumental aspects. The hollow metallic waveguides (HMW) presented here are manufactured using micro-machining techniques. Single-mode behavior has been investigated in laboratory through a technique of polarization analysis while transmission features have been measured using flux relative comparison. The single-mode behavior have been assessed at lambda=10.6 um for rectangular waveguides with dimensions a=10 um and b<5.3 um with an accuracy of ~2.5 %. The tests have shown that a single-polarization state can be maintained in the waveguide. A comparison with results on multi-mode HMW is proposed. Excess losses of 2.4 dB (~ 58 % transmission) have been measured for a single-mode waveguide. In particular, the importance of coupling conditions into the waveguide is emphasized here. The goal of manufacturing and characterizing the first single-mode HMW for the mid-infrared has been achieved. This opens the road to the use of integrated optics for interferometry in the mentioned spectral range.

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L. Labadie, P. Labeye, P. Kern, I. Schanen, B. Arezki, J. -E. Broquin. 2005-11-10. Modal Filtering for Nulling Interferometry-First Single-Mode Conductive Waveguides in the Mid-Infrared. https://doi.org/10.1051/0004-6361%3A20053407

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