Beam shaping of Bessel beams with high power laser systems

The continuous development of modern optical technologies enables progress in many areas of application. High-power laser systems play an important role in this, whereby progressively better beam qualities and higher laser powers are achieved and new fields of application are opened up. In this context, Bessel beams play a particular role due to their special properties, as they enable the decoupling of axial and lateral resolution. Due to the increased requirements and the increasing laser powers, new challenges arise in the conception, simulation and evaluation of the shaped laser beams, as well as for the laser systems themselves. The aim of this work is to deal with various sub-areas of these complex topics. This includes the reconstruction and evaluation of real laser beams by a laser-specific solution of the "transport of intensity" equation in order to reconstruct the field from intensity measurements of a laser beam along the beam waist. Subsequently evaluate the field, for example, by separating amplitude and phase and analyze perturbations with respect to ideal beams. Furthermore, this work contains the derivation of an analytical and efficient calculation of the axial intensity distribution of Bessel-Gauss beams in the framework of the Fresnel approximation, which are disturbed by typical wavefront errors like spherical aberration, astigmatism and coma. This allows such perturbed beams to be simulated and included already in the design and tolerance phase of such laser systems. The last part of the thesis is dedicated to the conceptual design of passively athermalized refractive high power laser systems. Here, concepts are presented that allow a significant reduction of laser power-dependent thermal shifts of focus positions by combining different materials and focal powers. Thus, systems can be designed for much higher laser power or systems can be stabilized regarding the applied laser power ranges.



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