神光Ⅲ原型装置终端靶场采用大口径取样光栅对透射的351 nm激光取样进行脉冲波形测试, 由于取样光聚焦点光线不是等光程的, 该取样方式将导致时间波形的畸变。建立了光栅全口径取样后聚焦的三倍频激光脉冲波形叠加模型, 模型考虑了激光光束近场强度分布和近场各点到聚焦点的光程变化两个主要影响因素, 研究了取样脉冲波形的叠加特性, 给出了该测量技术的适用范围和测量精度。结果表明, 对于取样光束口径为290 mm×290 mm,取样焦距为1380 mm,取样角为11.5°的基于光栅取样的脉冲波形测量系统, 只要被测激光脉宽大于1 ns, 取样后脉冲波形原始波形一致, 没有展宽。实验标定结果表明, 神光Ⅲ原型装置采用光栅取样对靶场三倍频激光脉冲进行测量是可行的, 该技术目前已经应用于原型装置。

Beam sampling by a fused-silica grating, which sampling the full-aperture beam, is focused on a diagnostics sensor to measure the laser pulse shape of technical integration lines of Shenguang-Ⅲ. The optical path of sampling beam at focus spots is not equal, so the pulse shape is different from the original pulse. Research on laser temporal profile measurement by means of grating are reported. The model to reconstruct the pulse shape is developed to study the superposition of sampling pulse, and spatial uniformity and optical path are considered. Simulation indicated that sampling has only a small impact on the pulse shape of beam, which aperture is 290 mm×290 mm, pulse duration is more than 1 ns, focus length of sampling beam is 1380 mm, and the angle is 11.5°. The calibration results show that the diagnostic technology of sample with grating is feasible for laser measurement. The technology is a great success in the laser temporal diagnostic of technical integration lines of Shenguang-Ⅲ.