@article{PuesLaubeFischeretal.2021, author = {Pues, Patrick and Laube, Michael and Fischer, Stefan and Schr{\"o}der, Franziska and Schwung, Sebastian and Rytz, Daniel and Fiehler, Torben and Wittrock, Ulrich and J{\"u}stel, Thomas}, title = {Luminescence and up-conversion of single crystalline Lu3Al5O12:Pr3+}, series = {Journal of Luminescence}, volume = {234}, journal = {Journal of Luminescence}, doi = {10.1016/j.jlumin.2021.117987}, pages = {117987 -- 117995}, year = {2021}, abstract = {This work deals with the spectroscopic properties of praseodymium doped single crystalline lutetium aluminum garnet (LuAG:Pr3+). A special focus was set on temperature- and time-dependent spectroscopy. Beyond the well-known down-conversion luminescence of LuAG:Pr3+, also UV-A/B up-conversion luminescence under excitation with a 488 nm laser was thoroughly investigated. Furthermore, the results of the spectroscopic investigations on the single crystalline material were supplemented and compared with measurements on a microscale powder sample. In addition, to the spectroscopic investigations, mechanistic considerations are presented to obtain a closer look at the up-conversion process in LuAG:Pr3+. We promote the thesis of a temperature-dependent energy transfer up-conversion mechanism.}, language = {en} } @book{OPUS4-1746, title = {Adaptive optics for industry and medicine. Proceedings of the 4th International Workshop on Adaptive Optics for Industry and Medicine}, editor = {Wittrock, Ulrich}, publisher = {Springer}, address = {Berlin}, isbn = {3-540-23978-2}, pages = {398}, year = {2005}, language = {en} } @article{Wittrock2010, author = {Wittrock, Ulrich}, title = {Laryngeally echolocating bats (Brief Communication Arising)}, series = {Nature}, volume = {466}, journal = {Nature}, doi = {10.1038/nature09156}, pages = {E6}, year = {2010}, language = {mul} } @incollection{VerpoortWittrock2009, author = {Verpoort, Sven and Wittrock, Ulrich}, title = {Miniaturized adaptive mirror for solid state laser resonators}, series = {Proceedings of the 7th International Workshop on Adaptive Optics for Industry and Medicine, Shatura, Russia}, booktitle = {Proceedings of the 7th International Workshop on Adaptive Optics for Industry and Medicine, Shatura, Russia}, year = {2009}, language = {en} } @misc{OPUS4-4711, title = {6th Laser Ceramics Symposium}, series = {Opt. Mat.}, volume = {34}, journal = {Opt. Mat.}, editor = {Wittrock, Ulrich and Kynast, Ulrich and J{\"u}stel, Thomas and Bredol, Michael}, publisher = {Elsevier B.V.}, pages = {935 -- 1002}, year = {2012}, language = {mul} } @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} } @article{Wittrock2014, author = {Wittrock, Ulrich}, title = {Limitations? What Limitations? Prof. Ulrich Wittrock, head of the Photonics Laboratory at the M{\"u}nster University of Applied Sciences, seeks out the ultimate boundaries of laser technology}, series = {Laser Community - the laser magazine from Trumpf}, volume = {02:14}, journal = {Laser Community - the laser magazine from Trumpf}, year = {2014}, language = {en} } @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} }