Holmium thin-disk laser at 2056 nm based on Ho: KYW/KYW epitaxy

Tm-doped monoclinic double tungstate crystals, KRE(WO 4 ) 2 or shortly KREW, are suitable for efficient multi-watt thin-disk lasers emitting at ∼1.9 μm [1] due to the high available doping levels and high transition cross-sections of the Tm3+ ions. Holmium (Ho3+) ions are attractive for laser emission above 2 μm due to the 5I 6 ↔5I 8 transition which is of interest for medical applications. KREW crystals are very suitable for Ho3+ doping [2] as well and efficient inband-pumped bulk Ho:KREW lasers have been demonstrated [3]. In the present work, we report on the first Ho:KREW thin-disk laser.