Abstract

High-power ultrafast laser systems working in 2-3-μm wavelength range continue to draw significant interest in the laser community due to the possibilities they open for nonlinear conversion, material processing, among others. Directly modelocked high-power thin-disk laser (TDL) oscillators are in this regard potentially interesting candidates for applications where MHz repetition rates and high pulse energy are beneficial. Early on, Kerr-Lens Modelocked (KLM) Ho:YAG TDLs demonstrated that they can achieve much higher powers in this wavelength region than other solid-state oscillator technologies, with the first demonstration of 18.4-W, 260-fs pulses at 2090-nm [1]. Recently, we confirmed this potential for power and energy scaling in this wavelength range by developing a SESAM-modelocked 50-W, 2-μJ system [2], representing, to the best of our knowledge, the highest output power and pulse energy from 2-μm single-oscillator, however, we were limited by the low modulation depth of the SESAM to rather long pulses > 1 ps. Although pulse compression methods can be applied; reaching shorter pulses from the oscillator is still a significantly more elegant and efficient option, in particular when combining with high pulse energies. So far, the highest achieved pulse energy and peak power reported from the 2-μm KLM TDL in this range are 0.24 μJ and 0.8 MW at an output power of 18.4 W [1]. In the current work we report a 0.5-μJ, 1.3-MW and 328-fs oscillator with an output power of 14 W, representing two-fold improvements in pulse energy and peak power in comparison to previously demonstrated state-of-the-art Ho:YAG KLM results, limited by gain narrowing due to intracavity losses. In the near future, it will be straightforward to reach μJ-levels of pulse energies and several MW of peak power directly from the modelocked 2-μm oscillator.

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