The NULLTIMATE test bench: achromatic phase shifters for nulling interferometry

The NULLTIMATE project developed and realized three concepts of achromatic phase shifters for nulling interferometry. One of the concepts is based on dispersive plates made of three materials which where fully characterized regarding their refractive index and thermo-optic behavior between 100K and 330 K. The other two concepts are based on mirror optics, one of which uses the phase shift of π when crossing a focus, the other the reversal of electric fields at reflection. An optical bench has been set up to test and characterize these phase shifters at wavelengths 2 − 2.4 μm with the option of changing to the 10 μm domain. We summarize the development of the achromatic phase shifters and report on the current status of the test bench.