TY - BOOK ED - Wittrock, Ulrich T1 - Adaptive optics for industry and medicine. Proceedings of the 4th International Workshop on Adaptive Optics for Industry and Medicine Y1 - 2005 UR - https://www.springer.com/de/book/9783540239789 SN - 3-540-23978-2 PB - Springer CY - Berlin ER - TY - CHAP A1 - Wittrock, Ulrich A1 - Welp, Petra T1 - Adaptive laser resonator control with deformable MOEMS mirrors T2 - MEMS/MOEMS Components and Their Applications III, Proc. SPIE N2 - 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. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-6537 VL - 6113 SP - 61130C PB - SPIE ER - TY - JOUR A1 - Heuck, Hans-Martin A1 - Neumayer, Paul A1 - Kühl, Thomas A1 - Wittrock, Ulrich T1 - Chromatic aberration in petawatt-class lasers JF - Appl. Phys. B N2 - In order to avoid optical damage and non-linear effects, high-power, high-energy lasers of the petawatt class like PHELIX (petawatt high-energy laser for heavy-ion experiments) use large-aperture optics. Usually, chromatic aberration associated with these optical elements is neglected. By means of numerical simulations, we show how the chromatic aberration affects the focal intensity pattern. In particular, we make quantitative predictions of how chromatic aberration decreases the focused peak intensity. Furthermore, we prove the feasibility of a new interferometer that measures the temporal pulse front distortions which arise from expansion telescopes. We also propose a scheme that pre-compensates these distortions. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-6523 VL - 84 SP - 421 EP - 428 PB - Springer ER - TY - JOUR A1 - Buske, Ivo A1 - Wittrock, Ulrich T1 - Diffraction analysis of aberrated laser resonators JF - Appl. Phys. B N2 - A numerical analysis of laser resonators with aberrations is presented. {T}he analysis shows that aberrations lead to large diffraction losses of laser resonators which are laid out to produce diffraction-limited beam quality. {S}tatic or dynamic compensation of the aberrations is possible and would yield much higher output power. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-8252 VL - 83 SP - 229 EP - 233 ER - TY - CHAP A1 - Heuck, Hans-Martin A1 - Wittrock, Ulrich A1 - Fils, Jérome A1 - Borneis, Stefan A1 - Witte, Klaus A1 - Eisenbart, Udo A1 - Javorkova, Dasa A1 - Bagnoud, Vincent A1 - Götte, Stefan A1 - Tauschwitz, Andreas A1 - Onkels, Eckehard T1 - Adaptive optics at the PHELIX laser T2 - Adaptive Optics for Laser Systems and Other Applications, Proc. SPIE N2 - 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. Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-6215 VL - 6584 SP - 658402 PB - SPIE ER - TY - CHAP A1 - Verpoort, Sven A1 - Wittrock, Ulrich T1 - Miniaturized adaptive mirror for solid state laser resonators T2 - Proceedings of the 7th International Workshop on Adaptive Optics for Industry and Medicine, Shatura, Russia Y1 - 2009 ER - TY - CHAP A1 - Verpoort, Sven A1 - Welp, Petra A1 - Wittrock, Ulrich T1 - Novel unimorph deformable mirror for solid state laser resonators T2 - MEMS Adaptive Optics III, Proc. SPIE N2 - We present a novel unimorph deformable mirror with a diameter of only 10 mm that will be used in adaptive resonators of high power solid state lasers. The relationship between applied voltage and deformation of a unimorph mirror depends on the piezoelectric material properties, layer thicknesses, boundary conditions, and the electrode pattern. An analytical equation for the deflection of the piezoelectric unimorph structure is derived, based on the electro-elastic and thin plate theory. The validity of the proposed analytical model has been proven by numerical finite-element modelling and experimental results. Our mirror design has been optimized to obtain the highest possible stroke and a high resonance frequency. Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-6504 VL - 72090N PB - SPIE ER - TY - JOUR A1 - Wittrock, Ulrich T1 - Laryngeally echolocating bats (Brief Communication Arising) JF - Nature Y1 - 2010 U6 - http://dx.doi.org/10.1038/nature09156 VL - 466 SP - E6 ER - TY - CHAP A1 - Verpoort, Sven A1 - Wittrock, Ulrich T1 - Unimorph deformable mirror for telescopes and laser applications in space T2 - International Conference on Space Optics (ICSO), Rhodes Island, Greece N2 - Over the past 5 years we have developed a new type of unimorph deformable mirror. The main advantages of this mirror technology are · very low surface scattering due to the use of superpolished glass · excellent coatings, even suitable for high power lasers, can be applied · active diameter of the mirrors can be between 10 mm and 100 mm · large strokes can be achieved even for small mirror diameters · integrated monolithic tip/tilt functionality based on a spiral arm design We have modeled these mirrors by analytical models as well as by the finite element method. This allows us to quickly design new mirrors tailored to specific applications. One example is a mirror for laser applications that has a diameter of 10 mm and can achieve a stroke in defocus mode of 5 μm. The stroke for these mirrors scales as the square of the mirror diameter, meaning that we can achieve, for example, a stroke of 125 μm for a mirror of 50 mm diameter. We will present design criteria and tradeoffs for these mirrors. We characterize our mirrors by the maximum stroke they can deliver for various Zernike modes, under the boundary condition that the Zernike mode has to be created with a certain fidelity, usually defined by the Maréchal criterion. Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-6484 UR - www.icsoproceedings.org PB - SPIE ER - TY - JOUR A1 - Verpoort, Sven A1 - Wittrock, Ulrich T1 - Actuator patterns for unimorph and bimorph deformable mirrors JF - Appl. Opt. N2 - 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. Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:836-opus-6490 UR - http://www.opticsinfobase.org VL - 49 SP - G37 EP - G46 PB - OSA ER -