Numerical Simulation of the Propagation of Pulse Bursts in Fiber Amplifiers With Multiple Timescales

To predict the behavior of high-energy pulse bursts, fine numerical simulation of the propagation of signals and amplified spontaneous emission (ASE) in fiber amplifiers is needed. In this research, a novel theoretical analysis of Yb-doped fiber amplifiers (YDFA) by finite-difference time-domain (FDTD) methods is proposed. This study allows to independently take into account evolutions of signals and ASE between multiple amplification stages. Approaches of mitigating ASE are discussed. Among them, the study of the location of acousto-optic modulator (AOM) is analyzed for the first time. A 15-mJ burst is obtained with burst repetition rate of 1 kHz, and low-level ASE. Our work can bring new insights into the design of high-energy burst-mode Yb-doped fiber amplifiers.