高重复频率飞秒激光高效加工硬X射线复合折射透镜  

Efficient Fabrication of Compound Refractive Lens for Hard X-ray Using High-Repetition-Rate Femtosecond Laser

作　　者：何煦[1] 孟立民[1] 马云灿 林鹤 李军[1] 叶雁[1] He Xu;Meng Limin;Ma Yuncan;Lin He;Li Jun;Ye Yan(Institute of Fluid Physics,China Academy of Engineering Physics,Mianyang 621900,Sichuan,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201204,China)

机构地区：[1]中国工程物理研究院流体物理研究所,四川绵阳621900 [2]中国科学院上海高等研究院,上海201204

出　　处：《中国激光》2024年第16期287-295,共9页Chinese Journal of Lasers

基　　金：冲击波物理与爆轰物理重点实验室基金(2021JCJQLB05707);中国工程物理研究院发展项目(TCGH0610)。

摘　　要：复合折射透镜(CRL)具有结构紧凑、焦距可调、准直方便等优点,是硬X射线自由电子激光(XFEL)光束聚焦的关键元件。目前,低能段X射线光束聚焦最常使用的金属铍(Be)材料CRL,由于抗热载性能差、力学强度低、散射严重等原因,不满足高能段X射线光束聚焦的实际应用需求。针对该问题,选择抗热载性能强、力学强度高、散射不严重的碳化硅(SiC)晶体材料作为基底,开展了抛物柱孔型SiC CRL的几何结构设计、飞秒激光加工、聚焦性能检测等三个方面的工作。研究结果表明:(1)在加工效率方面,高重复频率飞秒激光可实现抛物柱孔型SiC CRL的高效加工,由9个透镜单元组成的SiC CRL的加工耗时少于10 h;(2)在聚焦性能方面,利用高重复频率飞秒激光加工的抛物柱孔型SiC CRL,可将尺寸为170μm×55μm、能量为12 keV的硬X射线光束聚焦为170μm×10μm大小。Objective A compound refractive lens(CRL)is a kind of X-ray-focusing optical component comprising multiple concave lens units based on the refraction principle.It exhibits the advantages of compact geometric structure,adjustable focal length,and convenient collimation.This makes the CRL an important element for focusing hard X-ray beams delivered from X-ray free electron laser(XFEL)facilities.Given their excellent heat dissipation performance,diamond and silicon carbide(SiC)are considered as the preferred materials for CRL.However,manufacturing special surface contours(such as CRL with parabolic cylinder holes)on superhard materials,while ensuring processing accuracy and efficiency,is an urgent problem that requires a solution.Compared to common processing methods,femtosecond laser processing utilizes several characteristics,including“ultra-narrow pulse duration to avoid or reduce thermal effect,”“ultra-high peak power density exceeding the optical damage threshold of any solid material,”and“ultra-small focal spot size with Gaussian profile to achieve precision removal or modification of material,”to realize nearly“heat-free”micro-zone precision removal of materials.Therefore,with precise optimization of the processing strategy and controllable adjustment of laser parameters,a femtosecond laser can realize CRL fabrication on super-hard materials such as diamond and SiC.These materials are ideal for high-precision machining technologies for optical components,which are required for focusing hard XFEL beams.Methods Using a high-repetition-rate femtosecond laser(with the center wavelength of 1030 nm,pulse duration of 400 fs,maximum single pulse energy of 200μJ,and repetition rate of 200 kHz)alongside a 3D programmable precision machining platform(with a 3D precision motion stroke of 100 mm×100 mm×50 mm,absolute positioning accuracy of±0.3μm,and repetitive positioning accuracy of±0.03μm),a CRL array with parabolic cylinder holes is fabricated.This array features an opening diameter of 500μm an

关 键 词：飞秒激光 精密加工 复合折射透镜 碳化硅 X射线 

分 类 号：O436[机械工程—光学工程]