Lasing in a Tm : Yb3Al5O12 crystal pumped at 1.678 μm

The Yb₃Al₅O₁₂ (YbAG) crystal is proposed as a matrix of Tm³⁺-doped laser elements for two-micron lasers. A Tm : YbAG crystal of high optical quality is grown by the Czochralski method and its spectral and luminescent characteristics are studied. The luminescence decay time for the upper laser level ³F₄ is measured to be 4.7 ms. Lasing in this crystal pumped by a 1.678-μm fibre laser is obtained at a wavelength of 2.02 μm for the first time. The total and slope efficiencies of the laser at room temperature and an output power up to 330 mW reach 33% and 41%, respectively.