Adaptive laser resonators

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 com�pensating 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.

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