Integrated optics for astronomical interferometry

Abstract

Abstract.We report laboratory and on sky characterizations of planar integrated optics beam combiners in the K ([2.0 µm; 2.4 µm]) and K ([2.02 µm; 2.30 µm]) bands. Because of the strong scientific interests of the K band, we have extended the integrated optics technologies available in the telecom range (i.e. at 0.8 µm, 1.3 µm and 1.5 µm) to 2.0-2.5 µm. Ion exchange components optimized for these atmospheric bands provide stable contrasts higher than 95% with a laboratory white-light source and global throughputs of 35% in this spectral range. These results are completed with first stellar interferograms obtained with a silica-on-silicon two-way beam combiner on the IOTA interferometer. We characterized in the H and K bands the throughput of this beam combiner optimized for the H band ([1.47 µm; 1.78 µm]). On-sky fringes obtained on ιAur in the H and K bands clearly demonstrate a high instrumental contrast (larger than 50%) in both bands. This shows that integrated optics works with high performance outside its usual wavelength domain and provides good solutions for astronomical interferometry in a large wavelength range. We have measured single-mode ranges over 1 µm on our components which would allow to observe in two spectral bands simultaneously or to integrate both metrology reference and science signals in a single chip for astrometric applications.

Astrophysics in 2002

“…Berger et al (2001) provide lots of details on how you combine beams and such when looking at 4 Ori (not an Alpha, you notice), and there are more details from Laurent et al (2002) looking at i Aur.…”

Ion-exchanged glass waveguide technology: a review

“…A series of papers studied this approach using ion-exchanged waveguide devices as an enabling technology: first, proposing the approach and developing the concept 170 feasibility was demonstrated in laboratory with off-the-shelf components 171 and characterization of a beam combiner validated the technology, 172 followed by astronomical interference observations 173 at 1.6-μm wavelength and then by development of new waveguide devices for longer wavelength (2.0 to 2.5 μm) observations. 174 In astronomy, there is high interest in going further to midinfrared spectrum, 175 and ion-exchanged waveguides have been demonstrated in germanate glasses targeting the 3 to 4-μm spectral range. 176,177 Here, ion exchange has been a potential fabrication technology for final realization of such applications, but also to some extent an available platform for carrying out scientific experiments.…”

First results from the ESO VLTI calibrators program

“…3). Note that at the time of writing another beam combiner is being used with VINCI, based on integrated optics (IONIC, Laurent et al 2002;Le Bouquin et al 2004). IONIC is available in two versions, that cover the H and the K bands respectively.…”