Passive Q-Switching of a Cladding Pumped Erbium–Ytterbium Co-Doped Fiber Laser Induced by the Kerr Effect

In this letter, we propose a passively Q-switched all-fiber laser and demonstrate how to utilize a multimode double-clad Erbium–Ytterbium co-doped fiber as an active medium. The Q-switching is obtained based on the Kerr effect of multimode interference, which induced intensity modulation inside the linear cavity laser. Stable Q-switched pulses are obtained at 1552.3 nm with the repetition rate varying from 50.3 to 222.2 kHz, when the pump power is changed in the range from 1.00 to 3.09 W. We record the minimum pulse width and the maximum pulse energy at 2.1 μs and 2.7 μJ, respectively, at a pump power of 2.42 W. This proves a new modulation mechanism for obtaining high energy pulses based on all-fiber linear cavity.