Untitled - Laboratoire d'Astrophysique de l'Observatoire de Grenoble

Figure 11.8: Left panel: Process flow of Hollow Metallic Waveguides (HMW) manufacturing. I: Silicon 4
inches wafer - II: Guide definition by photo-lithography and RIE - III: Thermal oxidation and gold deposition -
IV: Gold and silica wet etching - A: P yrex T M 4 inches wafer - B: Photo-lithography and P yrex T M wet etching
- C: Gold deposition - D: Photo-resist stripping - F: Anodic bonding. Middle panel: photograph of a HMW
input using Scanning Electron Microscope. The Pyrex cover is maintained by anodic bonding on the silicon
substrate. The etching depth is equal to 10 µm. The gold deposition is thicker on the bottom part of the
wave-guide with respect to the lateral walls. Right panel: diffraction-limited spot corresponding to the output
flux of the waveguide at 10.6 µm. X axis in pixels. From Labadie et al., 2005, A&A, in press.
Spectro-Polarimetric Interferometry To address the promising issue of obtaining spectro-polarimetry at
the milliarcsecond angular resolution, we have been involved both in the theoretical modelling of the interferometric
observables in polarized light, and in commissioning the polarimetric mode of the French GI2T/REGAIN
interferometer (Rousselet-Perraut et al., 2005, A&A, submitted). Modelling the effect of instrumental polarization
on interferometric performances allows us to propose some recommendations for the VITRUV concept
(Sect. 11.2.3). K. Perraut (responsible) and J.B. Le Bouquin (PhD) are concerned.
Data processing Mainly within the AMBER project, but also within the VITRUV and DARWIN/PEGASE
studies, we have developed an expertise in interferometric data processing and in particular in single mode
interferometry (Tatulli et al., 2004, A&A, 418, 1179). We have developed a new algorithm to reduce AMBER
data (Millour et al., 2004, SPIE, 5491, 1222), but also other types of multi-axial data, using linear algebra
and generalizing the so-called ABCD algorithm. We have investigated the sources of biases due to atmospheric
jitter and the limits of the instruments in terms of field of view. This work has been mainly the work of PhD
students P. Mège, E. Tatulli, J.-B. Le Bouquin and F. Millour under the supervision of A. Chelli, F. Malbet
and G. Duvert.
11.2.5 JMMC and European Interferometry Initiative
The Jean-Marie Mariotti Center (JMMC) is an Expertise Center in Optical Interferometry, aiming at coordinating
the French efforts in high angular resolution. Initiated by LAOG and OCA in collaboration with a dozen
of other French laboratories, the JMMC has installed its coordination center at LAOG, where a project team
produces the “software instruments” needed in data reduction and analysis tools and in preparation software for
the new interferometric developments, especially for the VLTI. The contribution of LAOG has mainly consisted
in providing the software ASPRO to prepare interferometric observations. This software is originating from the
GILDAS suite where software has been developed for the radio interferometry at IRAM. The responsible for this
software is G. Duvert. A java-based interface has also been developed for an easy use by external astronomers.
This software has been complemented by the search of calibrators (searchCalib). ASPRO became the first
virtual observatory tool, since it searches the CDS catalogs to retrieve the information required to select good
interferometric calibrators. The software is adapted every semester to the new VLTI configuration provided by
ESO. Another task of LAOG staff is to provide support to JMMC users and is recognized as a CNAP duty.
There is a strong connection between the persons working on the projects or on the R&D and the ones
involved in JMMC. Some of them are indeed taking part to both activities.
This activity has naturally been extended at the European level where several members of our laboratory
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