title: Integrated Optics for Astronomical Interferometry. III. Optical Validation of a Planar Optics Two-Telescope Beam Combiner.
abstract: The optical characterization of a fiber-connected planar optics beam combiner dedicated to astronomical interferometry for two telescopes is presented. The beam combiner, fully integrated on a single 5 mm x 40 mm glass chip, is tested as the central part of an astronomical instrument. The single-mode waveguides are made by silver-ion-exchange technology upon glass substrates and provide spatial filtering, which improves the visibility measurement accuracy by selecting only the fundamental mode of the beams at the telescope focal plane. A global optical throughput of 43% is measured, and the sources of losses are identified and examined in detail. Solutions for improving this throughput are proposed. High and stable contrasts are obtained with a 1.55-mum laser diode (?96%) and with a white-light source (~92%) in the astronomical H filter (1.43 mum; 1.77 mum). The need for accurate control of differential instrumental polarization is demonstrated. In this context the intrinsic polarization-maintaining property of the planar optics component is characterized. This validation of the important potential uses of integrated planar optics should be valuable for future design of optical telescope arrays.
authors.forename: P
authors.initials: P
authors.lastname: Haguenauer
authors.forename: J P
authors.initials: JP
authors.lastname: Berger
authors.forename: K
authors.initials: K
authors.lastname: Rousselet-Perraut
authors.forename: P
authors.initials: P
authors.lastname: Kern
authors.forename: F
authors.initials: F
authors.lastname: Malbet
authors.forename: I
authors.initials: I
authors.lastname: Schanen-Duport
authors.forename: P
authors.initials: P
authors.lastname: Benech