Efficient graphene Q switching and mode locking of 1.34 μm neodymium lasers

We demonstrate that few-layered graphene sheets used as a saturable absorber can provide efficient Q-switching and mode-locking modulation in 1.34 mu m Nd:GdVO4 bulk lasers. The minimum Q-switched pulses were 450 ns for 260 mW average power, 43 kHz repetition rate, and 2.5 mu J pulse energy. For the mode-locked laser, an average power of 1.29 W was achieved with 11 ps pulse duration and 13 nJ pulse energy. To our knowledge, this average power is the highest yet obtained from a graphene mode-locked laser, and the corresponding optical-optical efficiency of 23% is the best result among 1.3 mu m neodymium mode-locked lasers. The quality factor M-2 of the Q-switched beam was 1.4 and 1.6 in the horizontal and longitudinal planes, respectively, and the M-2 of the mode-locked beam reached 1.1 and 1.0. These results clearly indicate the advantages of few-layered graphene as a saturable absorber. (C) 2012 Optical Society of America