The achromatic chessboard, a new concept of a phase shifter for nulling interferometry: IV. Advanced experimental measurements

International audienceContext. To characterize their atmospheres in order to find evidences of life, one has to detect directly photons from the exoplanets to measure their spectra. One possible technique is dark fringe interferometry that needs an achromatic pi phase shift in one arm of the interferometer. We have conceived a phase shifter made of two cellular mirrors, in which each cell position and phase shift is specific, so that the behaviour of the nulling with respect to wavelength is flat within a broad range. Aims. We want to validate experimentally two versions of this achromatic phase shifter: a transmissive one in bulk optics and a reflective one using a segmented deformable mirror. What we present in this paper are the last results obtained in the lab. Methods. We built an optical bench in the visible that allows us to test the principle and characterize the performances and the limits of this phase shifter. Results. We tested several transmissive and one reflective phase shifter and obtained, for instance, an attenuation of about 2.10-3 for a white source (from 430 to 830 nm) that proved the achromatic behavior of the phase shifter. The preliminary performances and limitations are analyzed