Growth and spectroscopic properties of the 2.9 μm Tm,Ho:LuYAG laser crystals

• Lu2.4Y0.6Al5O12 (LuYAG) crystals with different doping concentrations of Tm3+ and Ho3+ were grown by the Czochralski method.
• Absorption spectra indicate the Tm3+ can act as the sensitizer for Ho3+ and the crystals are suitable for 783 nm LD pumping.
• Results of fluorescence spectra and lifetimes suggest the Tm,Ho:LuYAG with 3 at.% Tm3+ and 1 at.% Ho3+ is promising to realize 2.911 μm laser output.

Lu2.4Y0.6Al5O12 (LuYAG) crystals with three different doping concentrations of Tm3+ and Ho3+ were grown successfully by the Czochralski method. The crystals exhibit broad absorption band at 783 nm and the full width at half maximum (FWHM) are about 11 nm. Excited by 783 nm laser diode (LD), strong fluorescence peaks are observed near 2.9 μm, suggesting that the Tm3+ ions can act as the sensitizer for Ho3+ ions. The stimulated emission cross-sections at 2.911 μm are calculated to be 5.49 × 10−18 cm2, 3.11 × 10−18 cm2, and 4.04 × 10−18 cm2, respectively. Compared with the Tm,Ho:LuAG, and Tm,Ho:YAG crystals, the Tm,Ho:LuYAG crystal with 3 at.% Tm3+ and 1 at.% Ho3+ has a relatively longer lifetime 0.138 ms for the upper level 5I6 and a shorter lifetime 7.25 ms for the lower level 5I7, which is advantageous to the population inversion. These results indicate that the Tm,Ho:LuYAG crystal with 3 at.% Tm3+ and 1 at.% Ho3+ is a new potential candidate for realizing the 2.911 μm laser output.