不同波形脉冲激光的时域误差对相干合成的影响

相干合成技术是实现高功率、高亮度光纤激光系统的重要技术途径.然而, 脉冲激光阵列中常常存在时域误差,这将影响脉冲激光的相干合成效果. 建立了脉冲激光存在时域误差时的相干合成理论模型,并在不同波形(方波、三角波、正弦波) 的脉冲激光存在时域误差时,对相干合成光束在远场的脉冲波形、峰值功率、 光强分布和桶中功率(PIB)等特性进行了数值计算和对比分析.计算结果表明: 方波脉冲激光相干合成光束的脉冲波形受时域误差影响严重,光强分布和PIB随着时域误差 的增大发生线性变化;三角波脉冲激光相干合成光束的脉冲波形和峰值功率受时域误差 影响严重,光强分布和PIB在时域误差较大时随着时域误差的增大发生较为剧烈的变化; 正弦波脉冲激光相干合成光束具有较好的输出特性,在两路正弦波脉冲激光相干合成中, 将两脉冲之间的时延控制在脉冲持续时间的10%以内,就能取得良好的合成效果.

Influence of temporal error with different pulse shapes on coherent beam combination system

Coherent beam combination of fiber laser array is an important technology for high-power output fiber laser systems. However, the coherent beam combination is influenced by temporal error, which always exists in the laser array. The coherent beam combination of pulse fiber lasers in the presence of temporal error is investigated in theory in this paper. The effects of pulse shape and temporal error on the coherently combined beam are studied. The characteristics of combined beam, i.e. pulse shape, peak power, far-field pattern and power in barrel (PIB) are calculated and analyzed when the pulse shapes (including square, triangle and sine) and temporal errors are different. It is revealed that for coherently combining square pulse lasers, the pulse shape of the combined beam changes acutely because of temporal error, and the far-field pattern and PIB change proportionally with temporal error increasing; for coherently combining triangle pulse lasers, the pulse shape and the peak power of the combined beam are acutely influenced by temporal error, and the far-field pattern and the PIB change acutely when temporal error is large. It is revealed that coherently combined beam of sinusoidal pulse lasers has good characteristics when two pulse laser with sinusoidal pulse shapes are coherently combined and the time delay between the two pulses is less than 10% of pulse duration.