Achromatic phase-shifter breadboard extensions

摘要

The Achromatic Phase shifter breadboard (APS) is designed for broadband (550-750 nm) nulling. This system has already been described in detail previously1,2, this paper describes improvements to the breadboard currently implemented and the corresponding results obtained. The breadboard improvements concern the following four points: A) Residual vibrations are compensated by active OPD control; B) Beam overlap can be optimized by an extra alignment mechanism; C) A more versatile detector/preamplifier is used; D) Adjustments of the phase shifter are now computer controlled. The paper describes the set-up and the results of these improvements on the nulling performance of the breadboard with the goal to achieve a 104 nulling ratio and to validate the computer simulations of the achromatic phase shifter. The validated value for nuldepth observed is currently 4600+/-400, and ratio's above 10,000 have been found, when measuring with a higher bandwidth. Nulldepths like these have to our knowledge not been reported before for relative spectral bandwidths of this magnitude. The program continues to optimize the setup and improve the results.