Three-dimensional photonic combiner for optical astro interferometry

We put forward an innovative scheme allowing multiple beam combination and closure-phase retrieval by means of a three dimensional array of coupled optical waveguides. Light propagation in an array of evanescently coupled waveguides is similar to conventional diffraction, however it is bound to a system with finite degrees of freedom. We have demonstrated that the latter feature allows relating uniquely the intensity pattern at the end of a 3x3 waveguide array to the amplitude and relative phases of three monochromatic fields coupled to suitable input waveguides. The method is scalable to arbitrary large arrays of telescopes and baselines.