  Thin-disk lasers (TDLs) have made spectacular progress in the last decades
both in continuous-wave and ultrafast operation. Nowadays, single thin-disk
oscillators with > 16 kW of continuous-wave (CW)-power have been demonstrated
and ultrafast amplifiers have largely surpassed the kilowatt milestone with
pulse energies in the multi-100 mJ range. This amazing development has been
demonstrated in the 1-{\mu}m wavelength range, using Yb-doped materials and
supported by industrially available components. Motivated by both strong
scientific and industrial applications, interest in expanding this performance
to longer wavelength regions continues to increase. In particular, TDLs
emitting directly in the short-wave mid-infrared (SW-MIR) region (2-3 {\mu}m)
are especially sought after, and although many early studies have been
reported, most remained in the proof-of-principle stage and the potential for
multi-100-W operation remained undemonstrated. Here, we report on our recent
results of a single fundamental-mode CW Ho:YAG thin-disk oscillator with >100 W
of power, surpassing previous single-mode TDLs by a factor of >4, and marking a
first milestone in the development of high-power SW-MIR TDLs. In optimized
conditions, our laser system emitting at {\guillemotright} 2.1 {\mu}m reaches
an output power of 112 W with 54.6-% optical-to-optical efficiency and an M2 =
1.1. This system is ideally suited for future direct modelocking at the 100 W
level, as well as for ultrafast amplification. We start the discussion with a
review of the state-of-the-art of TDLs emitting directly in the vicinity of 2
{\mu}m, and then discuss difficulties and possible routes both towards
ultrafast operation and next possible steps for power scaling.
