Recently, the team of Prof. Shuang-Chen Ruan and Prof. Chun-Yu Guo from Shenzhen University has developed a high-power femtosecond consisting of a 2.8 μm mode-locked Er:ZBLAN fiber oscillator, a single-mode Er:ZBLAN fiber preamplifier, and a large-mode-field Er:ZBLAN fiber main amplifier.
Based on the polarization state-controlled mid-infrared ultrashort pulse self-compression amplification theory and numerical simulation, combined with the nonlinear suppression and mode control method of the large mode field fiber, as well as the active cooling technology and double-ended pumping amplification structure, the system obtains a 2.8 μm ultrashort pulse output with an average power of 8.12 W and a pulse width of 148 fs, which further updates the highest international average power record originally achieved by the group. The system achieved an average power of 8.12 W with a pulse width of 148 fs for 2.8 μm ultra-short pulses, further refreshing the international record of the highest average power achieved by the group.
system is shown in Fig. 1. The preamplifier uses a 3.1 m-long single-mode double-clad Er:ZBLAN fiber as the gain fiber with a doping concentration of 7 mol.% and a core diameter of 15 μm (NA=0.12). The main amplifier uses a double-clad large-mode-field Er:ZBLAN fiber with a length of 4 m as the gain fiber with a doping concentration of 6 mol.% and a core diameter of 30 μm (NA=0.12). The larger core diameter results in a lower nonlinearity coefficient of the gain fiber, which is able to withstand a higher peak power as well as a pulse output with a larger pulse energy. Both ends of the gain fiber were fused with AlF3 end caps.
