Growth, characterization, and efficient laser operation of Czochralski- and micro-pulling-down-grown Yb³⁺:YScO₃ mixed sesquioxides

We report on the growth, spectroscopy and laser operation of Yb 3+ -doped mixed sesquioxide crystals. Various Yb 3+ -doped crystals with compositions close to (Y 0.5 Sc 0.5 ) 2 O 3 have been successfully grown by the Czochralski method and by the micro-pulling down (µ-PD) method. Our spectroscopic investigations reveal broadened stimulated emission and absorption cross-section spectra originating from the structural disorder of the mixed crystals. We find the peak wavelengths to shift by ∼1.6 nm between Y:Sc-ratios of 54:46 and 46:54 and confirm a linear relation of the peak position with the lattice constant of the host composition. In the laser experiments, we obtain highly efficient continuous-wave laser operation under pumping with an optically-pumped semiconductor laser (OPSL) at ∼975 nm, reaching slope efficiencies of up to 89% at optical-to-optical efficiencies exceeding 80% at laser wavelengths between 1037 nm and 1086 nm.