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为了增加19芯光纤激光器总输出光功率中共相位模式所占比例,提出两种改进方法,一是在掺镱光纤端面与反射镜面之间塔尔博特(Talbot)腔内引入三段具有一定间隔的非掺杂光纤,其结构尺寸和纤芯数值孔径均与掺镱光纤相同;二是将单模光纤激光器作为种子光源,利用透镜组对高斯光束进行束腰变换实现模式匹配,从而最大限度地激励共相位模式。基于速率方程组对改进后的方案进行了数值分析,计算了光纤端面间隔距离、信号输出端镜面功率反射系数和抽运功率对共相位模式功率所占总输出功率比例的影响。研究表明,在改进方案一中对于固定的镜面功率反射系数,存在最佳间隔距离以使共相位模式功率比例最大,共相位模式所占比例可以从改进前的79.06%提高到88.25%;通过改进方案二共相位模式所占比例可以提高到95.74%,从而确保了更好的光束质量。
In order to increase the proportion of the total phase optical power output of the 19-core fiber laser, two improved methods are proposed: one is to introduce three segments of Talbot cavity between the end face of the ytterbium-doped fiber and the reflecting mirror, Of the non-doped optical fiber, its structure size and core numerical aperture are the same with the ytterbium-doped optical fiber; the second is the single-mode fiber laser as the seed light source, the use of lens group Gaussian beam waist transformation to achieve pattern matching, so as to maximize Incentives in common mode. Based on the rate equations, the improved scheme is numerically analyzed, and the influence of distance between the fiber end facets, the power reflection coefficient at the signal output end and the pump power on the total output power ratio of the co-phase mode power is calculated. The results show that there is an optimal separation distance for the fixed specular power reflection coefficient in the improved scheme 1 to maximize the power ratio of the co-phase mode, and the proportion of the co-phase mode can be increased from 79.06% to 88.25% before the improvement; The proportion of the total phase mode option two can be increased to 95.74%, thus ensuring better beam quality.