Growth, spectroscopy, and laser operation of Ho ³⁺ :YScO ₃

We present crystal growth, spectroscopic investigations, fluorescence lifetime measurements, and laser performance of the Ho 3+ -doped mixed sesquioxide YScO 3 . Ho 3+ :YScO 3 crystals with various doping concentrations were grown by the Czochralski and the micro-pulling-down (µ-PD) methods. A comparative analysis with the parent compounds Ho 3+ :Y 2 O 3 and Ho 3+ :Sc 2 O 3 reveals that the optical properties of the mixed sesquioxides allow for tailored spectral tuning. Temperature-dependent spectra show broad absorption and emission bandwidths, with an enhanced gain cross section at cryogenic temperatures. The fluorescence lifetime was determined by the pinhole method to be as long as 9.4 ms for a sample with 0.5 at.% doping concentration. Crystals grown by both methods achieved laser slope efficiencies of up to ∼36% under 1907 nm Tm-fiber laser pumping. To the best of our knowledge, this is the first report on the growth and continuous-wave laser operation of Ho 3+ :YScO 3 crystals. Our studies demonstrate that Ho 3+ -doped mixed sesquioxides are promising candidates for 2.1-µm ultrafast lasers.