Nulling at TNO TPD: status update

TNO TPD has an extensive experience in the realisation of highly stable passive and active opto-mechanical systems. Future missions of ESA like DARWIN [1] rely heavily on these systems such as metrology equipment, delay lines, nulling equipment etc.. The nulling equipment will be used in the Nulling mode of DARWIN in which it will detect Earth-like planets around nearby stars. In the Nulling mode the starlight is dimmed to a factor of 10-6 at the wavelength range of 6 to 18 μm. During the recent years TNO TPD has been strongly involved in the development of nulling equipment such as phase shifters and a nulling breadboard. Also new concepts for nulling have been generated. A prism based phase shifter has been developed that operates in the visible. Nulling depths were achieved near 1000 in a wavelength range of 550 to 750 nm (equivalent DARWIN nulling depth: 105). Limiting effects like vibrations are presently being eliminated by including an optical path difference control loop. With the nulling breadboard a null depth of 400,000 was achieved and a stable null has been realised over several hours. Further work in the near future will be amongst others the phase A study of a nulling instrument GENIE that will operate on the ESO VLTI.