掺Yb^(3+)光纤激光器MOPA工作方式中的放大自发辐射

Amplified Spontaneous Emission of Yb^(3+)-Doped Fiber Laser Based on MOPA

为了研究光纤激光器工作中的自发辐射现象,从掺Yb3+光纤的能级结构和速率方程出发,建立主振荡功率放大(MOPA)光纤激光器的数学模型,对系统内各参量进行了数值计算。分析结果显示:在抽运工作稳态条件下,放大器的系统储能和自发辐射受到抽运强度和粒子掺杂浓度的影响;对于低重复频率的脉冲信号,放大过程中的自发辐射非常严重。为了减弱自发辐射,将连续抽运换成适当脉宽的脉冲抽运,即在信号脉冲前进行一段能够刚好让上能级粒子数充分恢复的脉冲抽运,可以在不影响信号脉冲放大的前提下,明显削弱连续抽运情况持续存在的自发辐射。数值模拟表明该方法在适当的抽运脉宽和强度下是可行的,实验数据则较为完好地印证了计算结果。

In order to research the phenomenon of spontaneous emission in fiber laser, the numerical model of master oscillator power amplifier （MOPA） systerm is established based on the energy-level structure and rate equation of Yba＋ -doped fiber. The analysis results by numerical calculation show that the system energy storage and amplified spontaneous emission （ASE） of amplifier are influenced by the pump power and particle population. The ASE is extremely serious in amplifying process with a low repetition rate. To reduce the ASE, continuous pump is changed to pulse pump, which means that a period of pump pulse that recovers the upper-level population adequately is set before the signal pulse. The ABE existing continuously in continuous pump system could be reduced obviously without influencing the signal pulse amplification. Numerical simulation shows that this method is feasible with a suitable pulse width and pump power, furthermore, the result of corresponding experiment agrees well with the calculation result.