The VSI/VITRUV combiner: a phase-shifted four-beam integrated optics combiner

We present a new four-telescope integrated optics (IO) beam combiner in the near-infrared H band, and preliminary photometric and interferometric measurements obtained in laboratory. The combiners tested and characterized in our experiments are at the heart of the VSI/VITRUV instrument, whose goal is to combine four to six telescopes of the VLTI. In this paper, we describe the combiners which incorporate phase-shifting devices and their characterization through the analysis of polarization properties, instrumental visibilities and phases. Our results were obtained with an eight-telescope laboratory interferometer, specially developed to simulate the VLTI. These results demonstrate one more time that the integrated optics technology is particularly well suited for interferometric combination of multiple beams, and therefore to achieve aperture synthesis imaging with the VSI/VITRUV instrument.