@article{Wittrock2014,
  author    = {Wittrock, Ulrich},
  title     = {Grenzen? Welche Grenzen? Prof. Ulrich Wittrock, Leiter des Labors f{\"u}r Photonik an der Fachhochschule M{\"u}nster, fragt nach den ultimativen Grenzen der Lasertechnik},
  series = {Laser Community - das Lasermagazin von Trumpf},
  volume    = {02:14},
  journal   = {Laser Community - das Lasermagazin von Trumpf},
  year      = {2014},
  language  = {de}
}
@inproceedings{WittrockWelp2006,
  author    = {Wittrock, Ulrich and Welp, Petra},
  title     = {Adaptive laser resonator control with deformable MOEMS mirrors},
  series = {MEMS/MOEMS Components and Their Applications III, Proc. SPIE},
  volume    = {6113},
  booktitle = {MEMS/MOEMS Components and Their Applications III, Proc. SPIE},
  publisher = {SPIE},
  doi       = {10.25974/fhms-653},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-6537},
  pages     = {61130C},
  year      = {2006},
  abstract  = {Adaptive laser resonators with deformable MOEMS mirrors under closed-loop control are discussed and experimental results are presented. The requirements for deformable mirrors and for closed-loop control systems of these mirrors are analyzed. Several deformable mirrors have been characterized and the results are presented. Currently available membrane mirrors deform under laser load and need further development before they can be used for aberration correction of solid state lasers above some tens of Watts. Nevertheless, the results are encouraging and the requirements are within reach of currently available technology. Finally, we demonstrate an Nd.YVO4-laser with a closed-loop adaptive resonator and more than 6 W of output power. The closed-loop system was able to compensate artificially introduced aberrations from a phase plate.},
  language  = {de}
}
@article{VerpoortWittrock2010,
  author    = {Verpoort, Sven and Wittrock, Ulrich},
  title     = {Actuator patterns for unimorph and bimorph deformable mirrors},
  series = {Appl. Opt.},
  volume    = {49},
  journal   = {Appl. Opt.},
  publisher = {OSA},
  doi       = {10.25974/fhms-649},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-6490},
  pages     = {G37 -- G46},
  year      = {2010},
  abstract  = {The actuator pattern of an adaptive mirror determines the amplitudes and the fidelities of the mirror deformations that can be achieved. In this study, we analyze and compare different electrode patterns of piezoelectric unimorph deformable mirrors using a numerical finite element model. The analysis allows us to determine the optimum actuator pattern, and it is also applicable to bimorph mirrors. The model is verified by comparing its predictions with experimental results of our prototype of a novel unimorph deformable mirror.},
  language  = {de}
}
@inproceedings{HeuckWittrockFilsetal.2007,
  author    = {Heuck, Hans-Martin and Wittrock, Ulrich and Fils, J{\´e}rome and Borneis, Stefan and Witte, Klaus and Eisenbart, Udo and Javorkova, Dasa and Bagnoud, Vincent and G{\"o}tte, Stefan and Tauschwitz, Andreas and Onkels, Eckehard},
  title     = {Adaptive optics at the PHELIX laser},
  series = {Adaptive Optics for Laser Systems and Other Applications, Proc. SPIE},
  volume    = {6584},
  booktitle = {Adaptive Optics for Laser Systems and Other Applications, Proc. SPIE},
  publisher = {SPIE},
  doi       = {10.25974/fhms-621},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-6215},
  pages     = {658402},
  year      = {2007},
  abstract  = {GSI Darmstadt currently builds a high-energy petawatt Nd:glass laser system, called PHELIX (Petawatt High-Energy Laser for Heavy-Ion Experiments). PHELIX will offer the world-wide unique combination of a high current, high-energy heavy-ion beam with an intense laser beam. Aberrations due to the beam transport and due to the amplification process limit the focusability and the intensity at the target. We have investigated the aberrations of the different amplification stages. The pre-amplifier stage consists of three rod-amplifiers which cause mainly defocus, but also a small part of coma and astigmatism. The main amplifier consists of five disk amplifiers with a clear aperture of 315 mm. These large disk-amplifiers cause pump-shot aberrations which occur instantly. After a shot, the disk amplifiers need a cooling time of several hours to relax to their initial state. This limits the repetition rate and causes long-term aberrations. We will present first measurements of the pump-shot and long-term aberrations caused by the pre- and the main amplifier in a single-pass configuration. In this context, we will present the adaptive optics system which is implemented in the PHELIX beam line and discuss its capability to compensate for the pump-shot and long-term aberrations.},
  language  = {de}
}
@article{RauschVerpoortWittrock2016,
  author    = {Rausch, Peter and Verpoort, Sven and Wittrock, Ulrich},
  title     = {Unimorph deformable mirror for space telescopes: environmental testing},
  series = {Opt. Expr.},
  volume    = {24},
  journal   = {Opt. Expr.},
  doi       = {10.25974/fhms-853},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-8530},
  pages     = {1528 -- 1542},
  year      = {2016},
  abstract  = {We have developed and manufactured a unimorph deformable mirror for space telescopes based on piezoelectric actuation. The mirror features 44 actuators, has an aperture of 50 mm, and is designed to reproduce low-order Zernike modes with a stroke of several tens of µm. We assessed the space compliance by operating the mirror in thermal vacuum, and exposing it to random and sinusoidal vibrations, as well as to ionizing irradiation. Additionally, the operational life time and the laser power handling capability were tested. The mirror was successfully operated in thermal vacuum at 100 K. We report on the conducted tests and the methods used to evaluate the mirror\&\#180;s performance, and discuss the compliance with the demanded requirements},
  language  = {de}
}
@inproceedings{RauschVerpoortWittrock2016,
  author    = {Rausch, Peter and Verpoort, Sven and Wittrock, Ulrich},
  title     = {Unimorph piezoelectric deformable mirrors for space telescopes},
  series = {Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, Proc. SPIE},
  volume    = {9904},
  booktitle = {Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, Proc. SPIE},
  doi       = {10.25974/fhms-923},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-9230},
  pages     = {990468},
  year      = {2016},
  abstract  = {We have developed, manufactured and tested a unimorph deformable mirror for space applications based on piezoelectric actuation. The mirror was designed for the correction of low-order Zernike modes with a stroke of several tens of micrometers over a clear aperture of 50 mm. It was successfully tested in thermal vacuum, underwent lifetime tests, and was exposed to random vibrations, sinusoidal vibrations, and to ionizing radiation. We report on design considerations, manufacturing of the mirror, and present the test results. Furthermore, we discuss critical design parameters, and how our mirror could be adapted to serve recently proposed space telescopes such as HDST and TALC.},
  language  = {de}
}