Growth, spectroscopy and laser operation of Yb3+,Na+/Li+-codoped CNGG-type garnets promising for ultrafast lasers

Rare-earth-doped calcium niobium gallium garnets (Ca3Nb1.5Ga3.5O12, 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 Yb3+,Na+ and Yb3+,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 Yb3+ 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.