Growth, spectroscopy and laser operation of Yb~(3+),Na~+/Li~+-codoped CNGG-type garnets promising for ultrafast lasers

摘要

Rare-earth-doped calcium niobium gallium garnets (Ca_3Nb_(1.5)Ga_(3.5)O_(12), shortly CNGG) are disordered laser materials attractive for ultrashort pulse generation. We report on the crystal growth by the Czochralski method, spectroscopy and efficient laser operation of Yb~(3+),Na~+ and Yb~(3+),Na~+,Li~+-codoped CNGG-type crystals. Their cubic structure is confirmed by X-ray diffraction and Raman spectroscopy. The absorption / stimulated-emission cross-sections and lifetime of Yb~(3+) are determined. Continuous-wave (CW) laser experiments are performed in a compact cavity using a 968-nm InGaAs pump laser diode. A 11.9 at.% Yb,Na:CNGG crystal generated 3.74 W at 1069.9 nm with a slope efficiency of 56.5%. Yb,Na:CNGG is promising for sub-100-fs mode-locked lasers at ～1 μm.