@article{VerpoortBittnerWittrock2020,
  author    = {Verpoort, Sven and Bittner, Matthias and Wittrock, Ulrich},
  title     = {Fast focus-shifter based on a unimorph deformable mirror},
  series = {Applied Optics},
  volume    = {59},
  journal   = {Applied Optics},
  number    = {23},
  organization    = {Optical Society of America},
  issn      = {1559-128X},
  doi       = {10.1364/AO.397495},
  pages     = {6959 -- 6965},
  year      = {2020},
  abstract  = {On-the-fly remote laser processing plays an increasingly important role in modern fabrication techniques. These processes require guiding of the focus of a laser beam along the contours of the workpiece in three dimensions. State-of-the-art galvanometer scanners already provide highly dynamic and precise transverse x-y beam steering. However, longitudinal focus shifting ("z-shifting") relying on conventional optics is restricted to a bandwidth of a few hundred Hz. We have developed and manufactured a fast piezo-based z-shifting mirror with diffraction-limited surface fidelity providing a focus shift of 1z> 60 mm with an actuation rate of 2 kHz.},
  language  = {en}
}
@article{KazasidisVerpoortWittrock2020,
  author    = {Kazasidis, Orestis and Verpoort, Sven and Wittrock, Ulrich},
  title     = {Sensor for dynamic focus control of a deformable mirror},
  series = {Appl. Opt.},
  journal   = {Appl. Opt.},
  number    = {59},
  doi       = {10.1364/AO.392970},
  pages     = {5625 -- 5630},
  year      = {2020},
  abstract  = {We recently presented a novel unimorph deformable mirror which allows for dynamic focus shift with an actuation rate of 2 kHz. Such mirrors suffer from hysteresis and creep. Therefore, they have to be operated in closed-loop. For this purpose, we developed a defocus sensor based on an astigmatic detection system. In this paper, we present the sensor design and discuss its performance.},
  language  = {en}
}