基于锥面镜和筒形反射镜复合结构的径向偏振光会聚及级联纵向电场的形成  

Formation of Cascaded Longitudinal Electric Field and Convergence of Radially Polarized Light Based on Conical Mirror and Cylindrical Reflection Mirror

作　　者：谭诗文 李建郎[1] Ueda Ken-Ichi 

机构地区：[1]中国科学院上海光学精密机械研究所信息光学与光电技术实验室,上海201800 [2]中国科学院大学,北京100049 [3]日本电气通信大学激光研究所

出　　处：《中国激光》2017年第8期32-42,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金(61275206;61475166;61405226);上海市自然科学基金(14ZR1445200)

摘　　要：径向偏振光聚焦后可以产生很强的纵向电场。以此为出发点,首先依据基尔霍夫衍射理论,计算得到了径向偏振光经锥面镜会聚后所形成的横截面呈现零阶贝塞尔函数分布的纵向电场,分析了会聚区域光场的相干长度和横向宽度与入射光光斑尺寸、锥面镜的锥顶角以及锥面镜出射端半径的关系。在此基础上,提出采用锥面镜和筒形反射镜的复合结构,通过设计合适的锥面镜和筒形反射镜参数,实现纵向电场的级联,且电场呈周期性分布。分析了筒形反射镜的参数对所形成的级联纵向电场的横向宽度、周期和占空比等的影响。结果表明,当所采用的锥面镜的锥顶角为60°时,出射端半径和筒形反射镜的内径均为999.682λ(λ为波长),可以实现周期长度为1154λ、占空比为1的纵向电场的级联;当用于电子加速时,加速区长度甚至可达到米级。这种级联纵向电场的设计将进一步使得电子的加速区长度得到显著增加,为电子加速到更高能量提供了可能。The radially polarized light can be tightly focused and then forms a strong longitudinal electric field. The longitudinal electric field which follows the form of zero order Bessel function in cross section is calculated based on the Kirchhoff diffraction theory when radially polarized light is reflected and focused by a conical mirror. The relationships among spot size of incident light, cone-apex angle, radius of the exit end of conical mirror and coherent length and lateral width of the optical field of convergence region are analyzed. With these results, a hybrid structure consisting of a conical mirror and a cylindrical reflection mirror is proposed. When the appropriate parameters of conical mirror and the cylindrical reflection mirror are designed, the cascaded and periodic distribution longitudinal electric field is formed, and then the dependence of the related parameters （including lateral width, period and duty circle） of cascaded longitudinal electric field on parameters of cylindrical reflection mirror is discussed. Results show that a cascaded longitudinal electric field with periodic length of 1154,1 and duty circle of 1 is formed when the conical mirror has an cone-apex angle of 60° and the radius of the exit end and the inner diameter of cylindrical reflection mirror are both 999. 682,1 （,1 is the wavelength）. This simulation suggests that the acceleration zone length can even reach the meter level when it is used for electronic acceleration. The design of this cascaded longitudinal electric field will further increase the length of the electron acceleration region to a significant extent, which could accelerate the electronics to higher energy.

关 键 词：物理光学 径向偏振光 纵向电场 锥面镜 筒形反射镜 级联电子加速 

分 类 号：O436[机械工程—光学工程]