18-mJ pulse energy, 27-W average power, second harmonic generation in a Q-switched 49-core Yb-doped fiber laser

This work demonstrates the potential of Q-switched 7x7 Yb-doped multi-core fiber lasers in achieving efficient frequency doubling at 515 nm, delivering up to 18 mJ pulse energy at 1.5 kHz with 57% conversion efficiency. Further investigations will focus on scaling the green light outputs beyond 100-W, 50-mJ, as well as exploring third harmonic generation at 343 nm.