[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Power-Scaling Nonlinear-Mirror Modelocked Thin-Disk Lasers

摘要： High-power ultrafast laser sources constitute a key technology to a wide variety of scientific and industrial applications that benefit from the combination of high average power and sub-ps pulse duration. While coherently combined amplifier systems now deliver kW-level average powers, ultrafast thin-disk lasers (TDLs) remain of considerable interest as compact, low-noise laser sources delivering multi-hundred-Watts with excellent beam quality. These oscillators are usually modelocked using either of two well-established techniques: SESAM or Kerr-lens modelocking (KLM). Recently, we demonstrated the first TDL modelocked using the frequency-doubling nonlinear mirror (NLM). This technique relies on the combination of an intracavity χ(2) crystal used for second-harmonic generation (SHG) and a dichroic output coupler mirror (OC) that is highly reflective for the second harmonic (SH) and partially reflective for the fundamental wave (FW). The NLM device (SHG crystal + dichroic OC) thus provides a saturable reflectivity enabling modelocked operation. Our first NLM-modelocked TDL delivered <30 W with pulse durations >323 fs at a repetition rate of 17.8 MHz. Here we present a power-scaled NLM-modelocked TDL delivering 66 W and 430 fs pulses at 9.3 MHz, and up to 87 W and 586 fs pulses at 8.9 MHz. We thereby improve the output average power by a factor ≈3 and the peak power by a factor ≈5. This corresponds to 3 orders of magnitude more peak power than NLM results based on bulk-crystal lasers. We furthermore identify stable modelocking regimes that avoid Q-switching instabilities.