Browsing by Author "Röcker, Christoph"

Now showing 1 - 6 of 6

Open Access
Detrimental effects of period-chirped gratings in pulse compressors
(2023) Bienert, Florian; Röcker, Christoph; Dietrich, Tom; Graf, Thomas; Abdou Ahmed, Marwan
Open Access
Experimental analysis on CPA-free thin-disk multipass amplifiers operated in a helium-rich atmosphere
(2022) Bienert, Florian; Loescher, André; Röcker, Christoph; Graf, Thomas; Abou Ahmed, Marwan
Es wird der Einfluss von Helium als atmosphärisches Gas in Scheibenlaser-multipass-Ultrakurzpulsverstärkern untersucht.
Open Access
High-power, high-brightness solid-state laser architectures and their characteristics
(2022) Brauch, Uwe; Röcker, Christoph; Graf, Thomas; Abdou Ahmed, Marwan
The development of high-power diode lasers enabled new solid-state laser concepts such as thin-disk, fiber, and Innoslab lasers based on trivalent ytterbium as the laser-active ion, which resulted in a tremendous increase in the efficiency and beam quality of cw lasers compared to previously used lamp-pumped rod or slab lasers and the realization of ultrafast lasers with several 100 W or even kilowatts of average power. In addition to their beneficial thermo-optical properties, these architectures offer characteristic benefits making them especially suitable to obtain dedicated laser properties. This review article comprises milestone developments, characteristic challenges, and benefits, and summarizes the state of the art of high-power solid-state lasers with the focus on ultrafast lasers.
Open Access
Modelling of natural convection in thin-disk lasers
(2020) Dietrich, Tom; Röcker, Christoph; Graf, Thomas; Abdou Ahmed, Marwan
In this paper, we present a FEM-model that can be used to investigate the effects of thermally induced natural convection at the thin-disk laser crystal. Based on this simulation, we calculated the distribution of the refractive index of the ambient gas for the case of air and helium. By evaluating the optical path difference of a beam at normal incidence, the angular tilt (gas wedge) in the plane of the direction of convection as well as the spherical contribution (gas lens) was calculated for a set of different pump spot geometries and temperatures of the pumped area on the surface of the laser disk. Equations were derived that allow to simply calculate the tilt angle and the focal length of the gas lens for different temperatures of the disk and pump spot diameters for air as ambient medium.
Open Access
Process limits for percussion drilling of stainless steel with ultrashort laser pulses at high average powers
(2022) Brinkmeier, David; Holder, Daniel; Loescher, André; Röcker, Christoph; Förster, Daniel J.; Onuseit, Volkher; Weber, Rudolf; Abdou Ahmed, Marwan; Graf, Thomas
The availability of commercial ultrafast lasers reaching into the kW power level offers promising potential for high-volume manufacturing applications. Exploiting the available average power is challenging due to process limits imposed by particle shielding, ambient atmosphere breakdown, and heat accumulation effects. We experimentally confirm the validity of a simple thermal model, which can be used for the estimation of a critical heat accumulation threshold for percussion drilling of AISI 304 steel. The limits are summarized in a processing map, which provides selection criteria for process parameters and suitable lasers. The results emphasize the need for process parallelization.
Open Access
Simple spatially resolved period measurement of chirped pulse compression gratings
(2023) Bienert, Florian; Röcker, Christoph; Graf, Thomas; Abdou Ahmed, Marwan