Q-switched pulse generation by stimulated Brillouin scattering assisted four-wave mixing effect in erbium–bismuth co-doped multi-elements silica glass based optical fiber laser

Abstract

We demonstrate Q-switched pulse generation at the 1562.5 nm region by using a 70 cm long erbium–bismuth co-doped alumina–germania–hafnium–yttria silica glass-based fiber as a gain medium in a simple ring resonator configured without saturable absorber and optical isolator devices. The Q-switching was obtained based on a stimulated Brillouin scattering assisted four-wave mixing effect in the gain medium, which induced the intensity modulation mechanism. The laser produced a multi-wavelength output comb centered at 1562.6 nm with a peak-to-peak spacing of about 0.09 nm due to nonlinear effects. Stable Q-switched operation of a hafnia–bismuth–erbium co-doped fiber laser was obtained at a pump power range of 129–319 mW with the repetition rate varying from 45.9 kHz to 89.3 kHz and the pulse width ranging from 8.8 µs to 3.58 µs. A maximum pulse energy of 26.9 nJ at an average output power of 2.4 dBm was achieved. This demonstrates a new passive technique based on a highly nonlinear gain medium for realizing Q-switched all-fiber laser sources.