Beam steering in the THz range is attracting increasing attention with regard to communication (6G), sensor technology or imaging. Although various transmitter or reflector arrays have recently been developed for these purposes, their efficiency is still limited compared to simple metal reflectors. Combined beam steering and focussing requires a multi-actuator system that enables both rotational and linear displacement of mirrors in large working ranges. Multi-stable co-operative actuator systems basically fulfil these requirements. A prominent example is the primary mirror of the James Webb Space Telescope, which uses actuators to individually align hexagonal mirror elements. In this project, we are therefore focussing on the combination of cooperative, multi-stable linear and rotational actuators for adaptive optics for THz - ADOPT. ADOPT builds on our previous project Kick and Catch, in which we explored a bistable out-of-plane motion of a freely moving mass and a quasi-continuous tilt angle of spheres. The next steps will now be taken in ADOPT: We will integrate the mechanisms of kick and catch into a system with multiple stable positions. The individual elements will be arranged in an array to demonstrate the final system, an adaptive THz mirror. Each mirror element consists of a piston that can reach multiple vertical rest positions by a pulse-like acceleration from its initial position and a subsequent catch in the desired hovering position. At the upper end of the piston, a spherical cap with an attached hexagonal mirror is rotated by many small subsequent pulses. Seven of these elements are then arranged to form a module, which forms the basis for larger systems consisting of several modules. This enables synchronous deflection and refocussing by adjusting the curvature. Due to the long wavelength of the THz radiation, there are only low requirements for the imaging; what is important is a large field of view and the relative deflection of the individual mirrors. The system offers a combination of a linear system with piezoelectric kicking and magnetic trapping and an electrostatic tilting system. The setup will be highly miniaturised, including micro-actuators, multi-stability, internal sensors and controls. Four research groups are combining their expertise to tackle the challenges of ADOPT's cooperative drive concepts. Two partners, Ulrike Wallrabe and Martin Hoffmann, have been working on microactuators for a long time. Tamara Bechtold is an expert in numerical multiphysical modelling and simulation at component and system level. Finally, Christoph Ament is an expert in control theory, specialising in nanopositioning.
