Abstract

Cubic sesquioxides are known to exhibit a high thermal conductivity, allowing for efficient heat removal even at high laser output powers. Their relatively low phonon energies inhibit non-radiative decay processes relevant for near and mid-infrared lasers. Sesquioxide crystals doped with Ho³⁺, Er³⁺, Tm³⁺ or Yb³⁺ enabled highly efficient laser performance in continuous wave (CW) and mode-locked laser operation [1]. Yb³⁺-doped Lu₂O₃ is an ideal material for high-power thin-disk lasers in multimode CW operation [2] and enables the generation of ultrashort pulses at high average power levels [3]. However, its growth is challenging due to the high melting temperature of more than 2400 °C. As a result, high-quality sesquioxide crystals are not commercially available to date, despite successful growth results using the heat exchanger method (HEM) in the past [4].

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