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Preliminary Results with Integrated Optics at IOTA

From Pierre.Kern@obs.ujf-grenoble.fr Thu Nov 30 06:44:12 2000
Date: Thu, 30 Nov 2000 06:25:33 -0700
From: Pierre Kern
Subject: Preliminary results with integrated optics at IOTA

Thursday November 30th 2000,

After obtaining first fringes with an integrated optics (IO) component on Sunday (Nov 26th, 2000) morning at the IOTA interferometer (Mt Hopkins, Arizona), we observed two nights with a component from LEMO made by ion exchange and two nights with a component from LETI made by ion etching. The current night is our last observing night.

We succeeded in switching the two beam combiners on Tuesday afternoon with no instrumental modifications other than component replacement. Up to now, we have observed about 20 bright stars. We obtained fringes on the sky in the atmospheric H band (1.5-1.8 micrometers) using both IO components.

These results confirm the promises of the IO technology. Aside from the capacity to provide accurate visibility measurements, we have demonstrated its versatility by switching the instrumental configuration without technical difficulties.

Both tested components produce interference from the beams coming from two 45 cm telescopes on a 25 m baseline. The LEMO component provides one interferometric output and two photometric outputs for the photometric calibration on each telescope beam (see output attached image on the IR detector array). This component is based on Y-junctions. The LETI component provides two interferometric outputs and two photometric outputs (see also the attached figure). It is based on asymmetric couplers, which are optimized to insure the achromaticity of the component.

Preliminary data reduction shows an instrumental contrast greater than 80%. On the attached figure the fringe contrast is about 30-35%: 65% for the resolved object, 65% due to a photometric unbalance between the beams and 80% for the rest, i.e. beam combiner and remaining atmospheric effects.

The faintest star observed, HR4035, is a H=+1.5-mag star. Determing the magnitude limit was not considered as a priority in this run, since we cannot identify clearly the origin of the flux losses with the current experimental setup (interferometer plus beam combiner).

Jean Philippe Berger, Pierre Haguenauer, Pierre Kern, Fabien Malbet,
Rafael Millan-Gabet, Karine Perraut

The LEMO component provides one interferometric output and two photometric outputs for the photometric calibration on each telescope beam (see output attached image on the IR detector array). This component is based on Y-junctions.

The LETI component provides two interferometric outputs and two photometric outputs (see also the attached figure). It is based on asymmetric couplers, which are optimized to insure the achromaticity of the component.

IONIC (Integrated Optics Near-Infrared Combiner) is an integrated optics beam combiner, developed as a common R&D project by the Laboratoire d'Astrophysique de l'Observatoire de Grenoble and the Laboratoire d'Electromagnétisme, Micro-ondes et Optoélectronique (LEMO).

Last Updated 30 November 2000