FIRST 5T 3D: Interferometric performances of a laser written bream combiner for FIRST/SUBARU

The context of this work is to improve the performances of the FIRST instrument, already on-sky at SUBARU Telescope. In the framework of astrophotonics, in order to reduce crosstalk observed in planar photonic integrated circuits (PICs), and therefore increase the instrument’s stability and sensitivity, we have designed and fabricated a series of 3D laser-written optical chips with 5T beam combiners. These chips have been tested in the FIRST/SUBARU optical bench simulator at LESIA, injecting five inputs simultaneously and scanning the fringes using independent MEMS segments, inducing a relative OPD modulation. The results of this study, comparing the signature obtained for a single source (star) as compared to a binary, with different relative flux will be presented in this work. We will show that both polarizations are guided, with no crosstalk, and analyze the interferometric performances as a function of the source type, showing that the binary companion can be detected, and evaluate the detection limit