Growth, structure, chemical etching, and spectroscopic properties of a 2.9 μm Tm,Ho:GdYTaO4 laser crystal

• A 2.9 μm laser crystal Tm,Ho:GdYTaO4 (Tm,Ho:GYTO) is grown by the Czochralski method.
• The crystal has high crystalline quality.
• Chemical etching is employed to investigate the defect structure with KOH etchant.
• The spectra, level lifetimes are measured, and absorption transitions are assigned.
• The Tm-Ho energy transfer mechanism in GYTO is also demonstrated.

A new promising 2.9 μm Tm,Ho:GdYTaO4 (Tm,Ho:GYTO) laser crystal was grown by the Czochralski method. The full width at half maximum (FWHM) of X-ray rocking curve on the (0 1 0) face is only 0.05°, which indicates that the crystal has high crystalline quality. The structure parameters of Tm,Ho:GYTO crystal were determined by Rietveld refinement method. Chemical etching is employed to investigate the defect structure of Tm,Ho:GYTO crystal with KOH etchant. The absorption, emission spectra, and level lifetimes were measured, and the corresponding absorption transitions were assigned. The absorption cross-section at 790 nm was calculated to be 2.04 × 10−20 cm2 and maximum emission-cross section at 2932 nm was 2.05 × 10−20 cm2. The level lifetimes of 5I6 and 5I7 are 131 μs and 4.09 ms, respectively. Compared with other hosts, such as Ho:YAG, the shorter lifetime of 5I7 and long lifetime of 5I6 in the Tm,Ho:GYTO crystal are easier to realize population inversion. The Tm–Ho energy transfer mechanism in GYTO is also demonstrated.