Abstract

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 [1], 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) [2]. Recently, we demonstrated the first TDL modelocked using the frequency-doubling nonlinear mirror (NLM) [3, 4]. This technique relies on the combination of an intracavity c⁽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) (Fig. 1b). The NLM device (SHG crystal + dichroic OC) thus provides a saturable reflectivity (Fig. 1f) enabling modelocked operation. Our first NLM-modelocked TDL delivered <30 W with pulse durations >323 fs at a repetition rate of 17.8 MHz (Fig. 1a) [3].

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