Spectroscopy and 2.1 µm laser operation of Czochralski-grown Tm ³⁺ :YScO ₃ crystals

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We report on growth, temperature-dependent spectroscopy, and laser experiments of Tm 3+ -doped YScO 3 mixed sesquioxide crystals. For the first time, cm 3 -scale laser quality Tm 3+ :YScO 3 crystals with 2.2 at.% and 3.1 at.% doping levels were grown by the Czochralski method from iridium crucibles. We reveal that the structural disorder in the mixed crystals allows for broad and smooth spectral features even at cryogenic temperatures. We obtained the first continuous wave laser operation in this material at wavelengths around 2100 nm using a laser diode emitting at 780 nm as a pump source. A maximum slope efficiency of 45% was achieved using a Tm 3 + (3.1 at.%):YScO 3 crystal. Our findings demonstrate the high potential of Tm 3+ -doped mixed sesquioxides for efficient ultrafast pulse generation in the 2.1 µm range.