Lithium Niobate Active Beam Combiners: results of on-chip fringe locking, fringe scanning and high contrast integrated optics interferometry and spectrometry

The context of this work is the development of integrated optic beam combiners devoted to high contrast interferometry, in particular for exoplanet spectral characterization and future spatial missions, where the use of compact and light optical beam combiners ensures robustness and stability of the interferometric signal. Thus, the development of materials allowing light confinement in both polarizations, together with a good transparency from the visible to the mid-IR and able to achieve electro-optic modulation, in order to finely tune the relative phase of the interacting fields, is knowing a rapid development. Lithium Niobate is an electro-optical material allowing index, and thus optical phase modification, by application of an external electric field. It is also well known for waveguide realization in the visible, near and mid-infrared. Here we present results on near and mid-infrared beam combiners achieving different optical functions: a) three telescope AC beam combiner, devoted to phase closure studies; b) Phase locking and fringe scanning using double Mach-Zehnder concept. Optimization of the fringe contrast by real time on-chip phase and photometry balance and c) High Resolution Spectrometers in channel waveguides.