Integrated optics for astronomical interferometry

V. Extension to the band

¹ 
Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France 

² 
Institut de Microélectronique, Electromagnétisme et Photonique, BP 257, 38016 Grenoble Cedex 1, France 

³ 
Alcatel Space Industries, BP 99, 06156 Cannes La Bocca Cedex, France
⁴ 
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁵ 
Laboratoire d'Electronique, de Technologie et de l'Information, 17 rue des Martyrs 38054 Grenoble Cedex 9, France

Corresponding author: E. Laurent, Emmanuel.Laurent@obs.ujf-grenoble.fr

Received: 20 December 2001
Accepted: 14 March 2002

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.