Characteristics of three operation schemes in a passively mode-locked all fiber ring laser

摘要

We demonstrate a passively mode-locked all fiber ring laser based on all-solid Yb-doped Photonic Bandgap fiber (AS-Yb-PBGF) which is designed to simultaneously provide laser gain and anomalous dispersion. The laser is comprised of 0.42m AS-Yb-PBGF and a segment of single mode fiber (SMF). By varying the length of the SMF from 0.8m to 3.2m, three operation schemes, namely soliton operation, gain-guided soliton operation, and self-similarity operation, have been obtained by means of numerical simulations in split-step Fourier method in the ring laser. In the case of net anomalous cavity group-velocity dispersion (GVD) when the SMF is 0.8m, we obtain soliton pulse with the balance between the nonlinear self-phase modulation (SPM) and the anomalous GVD. The soliton pulse has the pulse duration of 355fs and the bandwidth of 1.9nm, corresponding to the time-bandwidth product of 0.33, nearly a transform-limited pulse. As the length of the SMF is changed to 2m, self-similar propagation is generated with the net cavity GVD of +0.014ps~2. The pulse has strong frequency chirp and high pulse energy up to 4nJ. The pulse duration is 2.5ps with the bandwidth of 2.1THz. To obtain gain-guided soliton, we change the SMF to 3.2m leading to a large net positive cavity GVD of +0.04 ps~2 and enforce the spectral limit of the gain fiber. A chirped gain-guided soliton pulse is observed with pulse energy of ～1nJ, the pulse duration of 2.5ps and the bandwidth of 2.5 THz.