Coherent beam combination of fiber laser phased array is a promising technique to achieve high-brightness laser output. In this paper, we focus on central-lobe energy enhancement of the combined beam in the far-field by theoretically and experimentally investigating the relationship between the power-in-the-bucket (PIB) of the combined beam in the far-field and the beamlets amplitude modulation in the near-field. We employ a 19-elements fiber laser phased array integrating adaptive fiber-optic collimators with a beamlet filling factor of 0.903 and achieve phase-locking and beamlet pointing correction among fiber lasers using the SPGD algorithm. The amplitude modulation applied to the tiled sub-apertures is used to control the shape of the emissive array's amplitude envelope to further change the PIB of the combined beam under the same total output power. According to theoretical analysis, the fiber laser phased array achieves PIB = 0.51 for a zero truncation ratio (Tr), which is increased to PIB = 0.57 for Tr = 1.3. Experimentally, we observe PIB = 0.49 for Tr = 0 and PIB= 0.56 for Tr = 1.3. The experimental results are in good agreement with the theoretical analysis, suggesting that the amplitude modulation is helpful for further improving the energy density of central-lobe.

中文翻译：

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19元光纤激光相控阵中基于子束调幅的中心瓣能量增强实验演示


光纤激光器相控阵相干光束组合是实现高亮度激光输出的一种有前景的技术。在本文中，我们通过理论和实验研究了远场组合光束的桶内功率（PIB）与远场组合光束的中心瓣能量增强之间的关系。近场中的子束幅度调制。我们采用集成自适应光纤准直器的19元光纤激光器相控阵，子束填充因子为0.903，并使用SPGD算法实现光纤激光器之间的锁相和子束指向校正。应用于平铺子孔径的幅度调制用于控制发射阵列幅度包络的形状，以在相同的总输出功率下进一步改变组合光束的PIB。根据理论分析，光纤激光器相控阵在零截断比（Tr）时达到PIB = 0.51，在Tr = 1.3时增加到PIB = 0.57。通过实验，我们观察到当 Tr = 0 时，PIB = 0.49；当 Tr = 1.3 时，PIB = 0.56。实验结果与理论分析吻合较好，表明调幅有助于进一步提高中心瓣的能量密度。