Optimization of ASE suppression in high efficiency Tm3+-doped pulsed all-fibered MOPA operating at 1908.12 nm

摘要

We proposed and demonstrated high efficiency Tm3+-doped pulsed all-fibered master oscillator power amplifier (MOPA) operating at 1908.12 nm with Amplified Spontaneous Emission (ASE) suppressed by optimizing the pumping power, seed laser power and fiber length. Considering the effect of pulsed seed laser and ASE on amplifier output characteristics, the amplifier gain and ASE suppression ratio under different conditions are simulated. Using an optimized length of 1.0 m large-mode-area (LMA) Tm-doped fiber (TDF) is used as amplifier fiber, the maximum average output power of 14.62 W (slope efficiency of 46.0%) with total amplifier gain of 24.66 dB is obtained when pumping power of 30.5 W and input signal laser power of 1.225 W. Meanwhile, ASE can be effectively suppressed with maximum ASE suppression ratio of 49.85 dB is obtained at the repetition frequency (RF) of 1 MHz and the duty cycle of 80%. Central wavelength of 1908.12 nm with linewidth of 0.65 nm and the beam quality of M-x(2) = 1.35 and M-y(2) = 1.51. This is, to the best of our knowledge, the maximum ASE suppression ratio in pulsed Tm3+ doped fiber laser by using acousto-optic (AO) external modulation operating at 1908.12 nm without filter.