Bibcode
Labadie, L.; Martín, G.; Anheier, N. C.; Arezki, B.; Qiao, H. A.; Bernacki, B.; Kern, P.
Bibliographical reference
Astronomy and Astrophysics, Volume 531, id.A48
Advertised on:
7
2011
Journal
Citations
23
Refereed citations
15
Description
Context. Observations of milliarcsecond-resolution scales and high
dynamic range hold a central place in the exploration of distant
planetary systems in order to achieve, for instance, the spectroscopic
characterization of exo-Earths or the detailed mapping of their
protoplanetary disc birthplace. Multi-aperture infrared interferometry,
either from the ground or from space, is a very powerful technique to
tackle these goals. However, significant technical efforts still need to
be undertaken to achieve a simplification of these instruments if we
wish to recombine the light from a large number of telescopes.
Integrated-optics concepts appear to be a suitable alternative to the
current conventional designs, especially if their use can be extended to
a higher number of astronomical bands. Aims: This article
reports, for the first time to our knowledge, the experimental
demonstration of the feasibility of an integrated-optics approach to
mid-infrared beam combination for single-mode stellar interferometry.
Methods: We fabricated a two-telescope beam combiner prototype
integrated on a substrate of chalcogenide glass, a material transparent
from ~1 μm to ~14 μm. We developed laboratory tools to
characterize in the mid-infrared the modal properties and the
interferometric capabilities of our device. Results: We obtain
interferometric fringes at 10 μm and measure a mean contrast V =
0.981 ± 0.001 with high repeatability over one week and high
stability over a time-period of ~5 h. We show experimentally - as well
as on the basis of modeling considerations - that the component has a
single-mode behavior at this wavelength, which is essential to achieve
high-accuracy interferometry. From previous studies, the propagation
losses are estimated to be 0.5 dB/cm for this type of component. We also
discuss possible issues that may impact the interferometric contrast.
Conclusions: The IO beam combiner performs well at the tested
wavelength. We also anticipate the requirement of a closer matching
between the numerical apertures of the component and the (de)coupling
optics to optimize the total throughput. The next step foreseen is the
achievement of wide-band interferograms.