High-power tunable laser operation of Ho:YScO₃ crystal at 2.1 µm

We report the Czochralski growth, spectroscopic characterization, and laser performance at 2.1 µm of a Ho:YScO₃ mixed sesquioxide crystal with a doping concentration of 0.4 at.%. Spectroscopic evaluation was performed based on room-temperature absorption and fluorescence measurements. Intensity parameters, radiative lifetime of the ⁵I₇ manifold, and spontaneous emission rates were calculated based on Judd-Ofelt theory. For the ⁵I₇ → ⁵I₈ transition near 2.1 µm, the emission cross-section was derived to be 4.06 × 10^-21 cm², with an exceptionally broad full width at half maximum spectrum of 210.14 nm. In the laser experiment, the laser delivers a maximum continuous-wave output power of 12.1 W with a slope efficiency of 31%. Wavelength tuning over 85 nm (2074-2159 nm) is demonstrated using a Lyot filter. These results establish Ho:YScO₃ crystal as a promising gain medium for high-power, broadly tunable, and potentially ultrafast 2.1 µm lasers.