光学元件表面缺陷相对位置分布对近场光束质量的影响

Influence of Relative Position of Optical Component Surface Defects on Near Field Beam Quality

针对高功率激光装置,光学元件表面不同分布形态的多个缺陷引起的子光束,在传输过程中会相互干涉叠加,引起光束质量发生复杂变化,因此有必要对缺陷的相对位置关系加以规范。基于光的衍射传输理论,研究了光学元件表面存在不同空间分布的划痕时光场调制的变化,以及划痕深度对调制光束近场分布的影响。结果表明,元件前后表面存在平行或垂直划痕时均会比单一划痕产生更加严重的光束调制,最大调制度可增至1.5倍,且划痕具有更严格的深度要求。研究结果为光学元件图形制备标准的补充及高功率激光装置大口径光学元件表面缺陷指标的确定提供了重要参考。

For high-power laser facility, sub-beams caused by multiple defects of opitcal component surface with different distributions interfere with each other in the transmission process, bringing about complex changes in beam quality. So it is necessary to make a clear limitation on relative position of defects. On the basis of the diffraction transmission theory, when there are scratches with different spatial distributions on the optical element surfaces, the changes of beam modulation are studied. The influence of scratch depths on the distribution of near field beam modulation is also taken into account. Results show that when two parallel or vertical scratches are on the same or different surfaces of an element. Both of them produce more serious modulation than single scratch, and the maximum modulation degree can be increased to 1.5 times. Meanwhile more strict requirements for scratch depth are put forward. The results can provide reference for the revision of optical element standard and the determination of defects specifications for large- diameter elements in high-power laser systems.