Continuous-wave and mode-locked operation of diode-pumped Yb-NaY(WO4)2

ABSTRACT We studied diode pumping of the locally disordered Yb-doped NaY(WO 4 ) 2 crystal. An a-cut 1.514-mm thick sample (6.9 at % Yb doping or 4.52×10 20 cm -3 ) was placed under Brewster angle in a z-shaped astigmatically compensated cavity, without any active cooling. It was oriented for pumping and emission in S -polarization ( E //c). Laser experiments were performed applying a high brightness laser diode as a pump source. The laser diode delivered up to 2.1 W of input power and the emission wavelength was selected in the broad absorption peak of Yb:NaY(WO 4 ) 2 around 961nm. Continuous-wave operation in the 1-P m range was obtained for output coupler transmission between 1% and 10%. A maximum output power of | 180 mW and slope efficiencies up to 30%, rela ted to the absorbed power, were achieved. For femtosecond mode-locked operation, a semiconductor saturable absorber mirror as well as two SF10 prisms were included in the cavity. Aligning the cavity for shortest pulses, we obtained stable passive mode-locking with pulse durations as short as 97 fs directly from the oscillator. Applying external compression, the pulse duration could be further reduced to 90 fs with a corresponding time-bandwidth-product of 0.321. The average output power amounted to 59 mW at a repetition rate of 90 MHz and the corresponding output spectrum was centered at 1044 nm