光纤非相干合成光束在湍流大气中的传输特性

Propagation Performance of Incoherent Combined Beams of Fiber Lasers in Atmospheric Turbulence

建立了高功率光纤非相干合成光束在湍流大气中的传输模型。综合考虑了准直系统、对准误差、光束抖动和大气湍流的影响，分析了单模、多模光纤光束非相干合成系统的传输特性。理论计算表明，在准直系统设计为最佳值时，功率为10kw的单模激光由准直系统导致的光束质量退化率约为10％，而光束质量膨因子为13、功率为30kw的多模激光，其光束质量退化率约为I％。对于数目都为六束，总功率分别为60kW、180kw的单模、多模光纤光束组成的非相干合成系统，在倾斜误差没有校正时，单模光束阵列较多模光束的传输特性优势随湍流强度的增大而降低。在传输距离为5～15km时，单模光束阵列倾斜误差完全校正时的到靶光强是无校正时的1．32倍左右，而多模光束阵列的到靶光强变化不明显。

The theoretical model of high-power fiber incoherent combined beams propagating in atmospheric turbulence is established, including single mode laser and multi-mode laser. The influences of collimating system, mechanical jitter and atmospheric turbulence are considered. The results show that the beam qualityrs degeneration ratio of 10 kW single mode fiber laser is 10 % resulting from the collimating system. And the ratio of 30 kW multi- mode fiber laser is 1%. For six incoherent combined beams without tip-tilt correction, the advantage in propagation performance of single mode beam decreases with the increase of the intensity of turbulence when the propagation distance is longer than 5 km. The maximum intensity gain due to tip-tilt correction of single mode beams is 1.32 times than without tip-tilt correction when the propagation distance is 5-15 km, while the gain of multi-mode beams is not obvious.