Astronomy & Astrophysics

Free access article

A&A 390, 1171-1176 (2002)
DOI: 10.1051/0004-6361:20020404

Integrated optics for astronomical interferometry

V. Extension to the $\vec{K}$ band

E. Laurent^{1, 2, 3}, K. Rousselet-Perraut¹, P. Benech², J. P. Berger^{4, 1}, S. Gluck⁵, P. Haguenauer¹, P. Kern¹, F. Malbet¹ and I. Schanen-Duport²

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

(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 $\mu$ m; 2.4 $\mu$ m] ) and K' ([ 2.02 $\mu$ m; 2.30 $\mu$ m] ) 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 $\mu$ m, 1.3 $\mu$ m and 1.5 $\mu$ m) to 2.0-2.5 $\mu$ m. 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 $\mu$ m; 1.78 $\mu$ m] ). On-sky fringes obtained on $\iota$ Aur 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 $\mu$ m 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.

Key words: techniques: interferometric

Offprint request: E. Laurent, Emmanuel.Laurent@obs.ujf-grenoble.fr

Integrated optics for astronomical interferometry

V. Extension to the band

V. Extension to the $\vec{K}$ band