针对惯性约束聚变(ICF)驱动系统特别是其终端光学系统对元件数和元件厚度的限制要求,利用衍射光学元件(DOE)易于集成的优点,提出一种在石英基片的两面分别曝光制作色分离光栅(CSG)和光束采样光栅(BSG)的新方法,仅需一个石英片即可同时实现谐波分离和光束采样的功能。分别采用光学制版和电子束直写的方法制作了色分离光栅和光束采样光栅的掩模,并利用离子束刻蚀的方法加工了色分离光栅一光束采样光栅集成元件。结果表明,此集成元件的三倍频光能量利用率、色分离度以及采样效率等参数均与三倍频光通过色分离光栅、光束采样光栅分离元件时得到的结果相吻合,达到了惯性约束聚变激光驱动器终端光学系统的基本技术指标要求。
Aiming at the restriction of the number and the thickness of elements used in the inertial confinement fusion (ICF) system, especially in the final optics assembly, and utilizing the characteristic of easy integration of diffractive optical element(DOE), a new means to fabricate color separation grating (CSG) and beam sampling grating (BSG) on two surfaces of one fused-silica substrate with two-surface exposure method is presented. Thus the functions of harmonic wave separation and beam sampling are realized through one silica plate. The masks of CSG and BSG are fabricated by photolithograph and e-beam direct writing method, respectively, and the ion beam etching method is used in fabricating the combined CSG-BSG element. The experimental results show that the parameters such as energy utilization ratio, color separation ratio and sampling efficiency for 300 harmonic wave are in accordance with those of separated CSG and BSG elements, which achieve the basic technical requirements of the final optics assembly of ICF driver.