3 µmにおけるホウ素ドープレーザーセラミックスの赤外線中間域における、音響エネルギー低減とイオン不活性化の相乗効果によるパワー増強

Direct high-power ∼3 µm mid-infrared (mid-IR) laser generation from Ho³⁺-doped oxides has long suffered from severe drawbacks including strong non-radiative losses due to high phonon energies, as well as disparity in fluorescent lifetimes between the laser up- and low-levels. Here, we propose a synergistic strategy to solve these problems by utilizing the low-phonon-energy Y₂O₃ sesquioxide ceramics to suppress multiphonon-assisted non-radiation relaxation, and co-doped Pr³⁺ as deactivators to promote the population inversion of Ho³⁺ activators. As a result, we successfully demonstrate the first mid-IR laser operation around 3 µm from Ho³⁺-doped ceramics and realize a maximum continuous-wave (CW) output power of 1.43 W. To the best of our knowledge, this result represents the highest CW output power among all Ho³⁺-doped active oxide materials in the 3 µm spectral region. This work will pave the way for mid-IR power scaling by low-cost and large-size laser ceramics and facilitate a wide range of new frontiers in ultrafast mid-IR photonics at new laser wavelengths.