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Adaptive laser resonators

Development of control strategies for adaptive high-power lasers using deformable mirrors for compensation of thermal disturbances and active beam shaping.

Description

High power lasers with output powers ranging up to several kW are an essential part in numerous industrial fabrication processes. Due to the high power and inevitable power losses, the laser resonator locally heats up. Especially the laser active material (laser crystal) is subject to high thermal load from the lasing process. The temperature change implies a change of geometry of the optical system. Consequently, the mode diameters change which leads to an undesired variation in the M2-value (Thermal lensing).

The objective of this project is to develop techniques for actively compensating thermal effects in high power lasers. For this purpose, an adaptive mirror inside the resonator which can be actively deformed is used. In a first place, a combination of two pneumatically actuated mrrors shall be used. In a later phase, a thermomechanically actuated mirror shall be developped and used for precise compensation. In a later stage of the project, the undesired effects inside the laser shall be compensated by the deformation of a mirror with more degrees of freedom inside the resonator. Thermal load can be applied to a mirror in the resonator in order to thermomechanically deform it. For this purpose, a control laser operating at a wavelenth for which the mirror is absorptive, can be used. The deformation of the mirror can be controlled by spacial modulation of the control laser. This can efficiently be achieved by a DLP (Digital light processing) chip.

Partner

This research project is a collaboration with the Institut for Laser Technologies at the University of Stuttgart (IFSW).

Publications

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  • K. Schmidt, P. Wittmüß, S. Piehler, M. Abdou Ahmed, T. Graf, O. Sawodny, "Modeling and Simulating the Thermoelastic Deformation of Mirrors Using Transient Multilayer Models",  Mechatronics, 2018..
  • K. Schmidt, P. Wittmüß, S. Piehler, M. Abdou Ahmed, T. Graf, O. Sawodny, "Modellierung optisch adressierter Spiegel für adaptive Hochleistungslaser",  at - Automatisierungstechnik, 2018.
  • S. Piehler, T. Dietrich, P. Wittmuess, O. Sawodny, M. A. Ahmed & T. Graf“Deformable mirrors for intra-cavity use in high-power thin disk lasers”Optics Express25pp. 4254-42672016doi:10.1364/OE.25.004254
  • P. Wittmuess, S. Piehler, T. Dietrich, M. A. Ahmed, T. Graf & O. Sawodny“Numerical Modelling of Multimode Laser Resonators”Journal of the Optical Society of America B33pp. 2278-22872016doi:10.1364/JOSAB.33.002278
  • P. Wittmuess, C. Tarín, A. Keck, E. Arnold & O. Sawodny“Parametric Model Order Reduction via Balanced Truncation with Taylor Series Representation”IEEE Transactions on Automatic Control (TAC)2016doi:10.1109/TAC.2016.2521361
  • K. Schmidt, P. Wittmüß & O. Sawodny, "On state estimation and reachability of linear PDE-BVP cascades with thermomechanical application", IEEE Conference on Decision and Control (CDC), Melbourne, Australia, 2017.
  • K. Schmidt, P. Wittmüß, S. Piehler, M. A. Ahmed, T. Graf & O. Sawodny“Modellierung thermomechanisch aktuierter, deformierbarer Spiegel für adaptive Optiken in Hochleistungslasern”GMA FA 1.30Salzburg, Austria2017
  • K. Schmidt, P. Wittmüß & O. Sawodny“Spectral Shift of Cylindrical Heat Equations by Full-State Boundary Feedback”IFAC World CongressToulouse, France2017

Coordinator

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M.Sc.

Kevin Schmidt

Research Assistant