We have investigated the manufacturing and characterization of first single-mode conductive waveguides to be used as modal filters for nulling interferometry in the mid-infrared range 4-20 μm . As a ...very high dynamic range is mandatory for the detection of Earth-like planets, modal filtering is a crucial instrumental aspect. The hollow metallic waveguides (HMW) presented here are manufactured using micro-machining techniques. Single-mode behavior has been investigated in the laboratory through polarization analysis and transmission features have been measured using relative flux comparison. Single-mode behavior was assessed at λ=10.6~μm for rectangular waveguides with dimensions a=10~μm and b≤5.3~μm with an accuracy of ~2.5%. The tests showed that a single-polarization state can be maintained in the waveguide. A comparison with results on multi-mode HMW is given. Excess losses of 2.4 dB (~58% transmission) have been measured for a single-mode waveguide. In particular, the importance of coupling conditions in the waveguide is emphasized here. The goal of manufacturing and characterizing the first single-mode HMW for the mid-infrared has been achieved. This opens the road to the use of integrated optics for interferometry in this spectral range.
This paper reports results obtained with the Very Large Telescope Interferometer Commissioning Instrument (VLTI-VINCI) where the fiber interferometric coupler MONA was temporarily replaced by an ...integrated optics beam combiner (IONIC). The two-beam combiner operating in the H atmospheric band was tested at Paranal during two weeks in July 2002. Fringes were recorded on several stars with the siderostats and the Unit Telescopes (UT). We demonstrate that integrated optics allows beam combination with a high interferometric efficiency, stability and spatial filtering. The instrumental visibility of VLTI+IONIC is better than 85%, which is just 5% under the visibility of the IONIC device alone. During this run, the flux injection in the IONIC combiner was not optimized since we used the K-band MONA optics. However, we obtain fringes with the 35 cm siderostats on a star of magnitude $mH=2.47$ ($\kappa^2$ Scl). It allows us to extrapolate a magnitude around $mH\sim6$ with 8 m telescopes without adaptive optics and in the same poor injection conditions.
In this work, we demonstrate the first implementation of an integrated optical magic T. Such structure is designed to give, at the output, the sum and the difference of its two input optical signals ...using the multimode interference phenomena. The structure is fabricated using the ionic exchange technology on glass. The first obtained results verify the function of the magic T.
The design of an
N×
N multi-mode interference coupler with weakly guiding condition is considered. Focus is put on the positioning of access waveguides. The best positions are obtained using ...eigenvectors overlapping requiring only a modal solver leading to a very short computation time as no propagation is required. Beyond its simplicity, it provides a clear physical understanding of the self-image theory when the multi-mode section is weakly guiding. This method computes in addition the tolerance on the access guide positioning. Results are in excellent agreement with those from literature.
We present in this paper the astronomical validation of a new approach to interferometric starlight combination. Using integrated optics technologies developed by the telecommunication industry, we ...have implemented optical circuits on coin-size chips that combine two beams and provide simultaneous photometric calibration signals. We report the first interferometric observations of stars using such beam combiners at the Infrared Optical Telescope Array (IOTA). This result opens the way to a new generation of miniaturized, high performance, and reliable instruments, dedicated to interferometric aperture synthesis.
PDF
