Static and dynamic mode evolution in high-power distributed side-coupled cladding-pumped fiber amplifiers

Abstract

We present a theoretical study of mode evolution in high power distributed sidecoupled cladding-pumped (DSCCP) fiber amplifiers. A semi-analytical model taking the side pumping schemes, transverse mode competition and stimulated thermal Rayleigh scattering into consideration has been built, which can model the static and dynamic mode evolution in high power DSCCP fiber amplifiers. The mode evolution behavior has been investigated with variation of fiber amplifier parameters, such as the pump power distribution, the length of the DSCCP fiber, the averaged coupling coefficient, the number of the pump cores, and the arrangement of pump cores. Interestingly, it revealed that static mode evolution induced by transverse mode competition is different from the dynamic ones induced by stimulated thermal Rayleigh scattering. It shows that the high order mode experiences slightly higher gain in DSCCP fiber amplifiers, but the mode instability thresholds for DSCCP fiber amplifiers are higher than those end-coupled counterparts. By increasing the pump core number and reducing the averaged coupling coefficient, the mode instability threshold can be increased, which

Metasurface-generating high purity narrow linewidth cylindrical vector beams: power scaling and its limitation

“…To find out the possible physical mechanism of the mode purity gradually degradation as the output power increasing, the impacts of the mode purity of laser source and the thermal-lens effect have been simulated. Due to the fact that the HOMs have stronger gain in fiber laser systems, the power fraction of HOMs increases as laser power increases [34,35]. The characteristics of CVBs generated from the LP 01 and LP 11 laser source has been list in Table 1.…”