Second-harmonic generation using a high-energy and tunable Q-switched multicore fiber laser

We demonstrate second-harmonic generation using a high-energy and tunable Q-switched Yb-doped seven-core fiber laser. The laser is tuned by incorporating a diffraction grating in the cavity, and is tunable over a range of about 40 nm with peak energy of more than 0.34 mJ at pulse repetition rate of 5 kHz. A conversion efficiency of about 7% is achieved using a 4/spl times/4/spl times/9 mm KTP crystal. Due to the tunability of the laser, a temperature-controlling oven is not needed for phase matching.