Ytterbium-doped Fiber Pulse Amplifier

Fiber lasers have the advantages of high conversion efficiency, large tuning range, ease of both integration and thermal management, so it is convenient to obtain high power, high brightness and excellent beam quality output. In the paper, according to the request of far-distance optical imaging, Ytterbium-doped fiber pulse amplifier was established to obtain a high peak-power and excellent beam quality pulsed laser. The main contents are as follows:1. The rate equation of the laser based on ytterbium ion energe level structure was established and theoretically analyzed. The master oscillating amplifier construction, pumping method and pumping coupling method were analyzed, respectively. According to the request of the subject, the forward end-pumped was chosen to achieve the laser amplification in the paper.2. The numerical simulation was established to analyze stimulated Brillouin scattering(SBS) and stimulated Raman scattering(SRS). The stimulation condition of both in pulsed fiber laser amplifiers were compared. The simulation results show that SBS and SRS do not occur in watt-level pulsed laser amplifiers. SBS must be considered only when the laser power is higher than tens of watts.3. The fiber amplifiers with weak signal and strong signal were studied, respectively. The optimized fiber length of single stage was obtained, and the optimized fiber length of one stage fiber amplifier with weak signal was chosen as 1.2m. In consideration of the absorbing effect of fiber length on pump laser and signal laser, the optimized fiber length of fiber amplifier with strong signal was chosen as 4.5m. By a optimized design of the fiber amplifier, laser pulse with an average power of 1.126 W was obtained, which has a gain of 11 and the maximum peak-power of 112.6 W. The results confirmed the feasibility of amplifying microwatt scale laser to watt scale laser, which satisfies the basic request of far-distance optical imaging.