During the first 20 years of TRUMPF’s existence as a laser company, it developed a reputation for standard products for applications, now referred to as the traditional industrial applications: laser cutting and welding of steel and aluminum. During the same time, TRUMPF acquired five basic technology platforms – fast-flow and diffusion-cooled CO2 lasers, thin disk, diode and fiber lasers. The standard products cover only a small section of the multi-dimensional parameter space that can be covered with these five basic technologies. These platforms, however, provide enormous flexibility and highly reliable building blocks that are now used to fill white areas in the parameter space, enabling novel applications unrelated to the original applications for these technologies. Presented are some examples of how the scaling of these technologies has led to unique and novel laser devices and applications. They include the generation of EUV with CO2 lasers, short-pulse applications with diffusion-cooled and fast-flow CO2 lasers for processing of composite materials and plastics. Laser output power, the traditional main characteristic for CO2 lasers, made way for pulse energies, pulse lengths and wavelength. The traditional cw thin disk laser platform was transformed into short and ultra-short pulse lasers with wavelengths down to 343 nm. Diode lasers evolved from low brightness pump sources for thin disk lasers to diode direct lasers. This flexibility will ensure that remaining white spaces in the parameter space can be filled in the future as required.
Modern high power industrial CO2 lasers are the result of decades of technological advancements aimed to improve laser parameters such as gain and saturation intensity to obtain the best power extraction efficiency. In this paper a resonator optimization approach is presented that includes laser power stability as one of the criteria for selecting the best configuration. This approach is applied to a hybrid stable-unstable annular RF excited CO2 laser.
The influence of a variety of parameters, such as the gas composition, pressure and lateral variation of Joule heat release
of the discharge at employed frequency, are taken into account to derive a distributed thermal lensing expression and to
numerically calculate the focal length as a function of position within the inter-electrode gap. The process of widening of
the beam inside the resonator is investigated by means of complex ray methodology. The findings are incorporated into
the optimization process of the optical resonator in the stable direction and the impact on the beam quality and power
stability is verified by experimental results.
A comprehensive investigation of the main parameters that determine the effective power scaling of diffusion cooled
annular CO2 lasers in the 3kW region is presented. Aspects such as RF excited discharge characteristics; small signal
gain, free space resonator configuration, beam stability and quality are discussed in detail. Simulations of the resonator
system are presented and different shapes for the azimuthal direction are evaluated for power and stability.
Presented is a study of a coaxial, hybrid-stable-unstable resonator for high power lasers. The coaxial configuration
allows the realization of the outcoupling and rear mirror in one mechanical structure with the incorporation of an axicon
mirror with retroreflective characteristics as an intra-cavity folding mirror. The design of the stable direction is
investigated to optimize the set-up for best beam quality and minimized alignment sensitivity. Additionally, the instable
direction is examined to achieve an even heat load on the mirrors. Simulations of the laser structure are performed and
compared to measurements.
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