光纤激光器空间相干合束远场特性分析

Analysis of far-field characteristics of spatial coherent beam combining fiber lasers

基于Fraunhofer标量衍射理论,计算了按圆周形排列的6束光纤激光相干合束的远场光强分布,并对其能量集中程度进行了讨论。分析表明合成光束的远场光强分布可等效于若干平面波干涉结果与单束衍射包络之积,当单元激光器所排列的圆周直径在5倍单元激光束腰宽度以下的时候,合成光束将有超过90%的能量落在单元光束的86.5%能量圆以内。结论指出适当选择单元激光器的排列间距可以控制能量的集中程度,甚至使合成光束的能量集中度优于原单元激光器产生的高斯光束。

The far-field intensity distribution of 6 circular arranged coherent fiber lasers is simulated numerically and its power convergence is estimated based on Fraunhofer diffraction theory. The results show that the intensity distribution at far-field is equivalent to the product of a Gaussian envelop and the interference distribution of several planar waves. When the diameter of the arranging circle is less than 5 times of the radius of a unit laser, over 90% of the power will drop into the 86.5% power circle of the unit laser. The calculation leads to the conclusion that power convergence of the combined beam can be optimized by adjusting the arrangement, where the convergence can even exceed that of a single unit laser beam.