Airy加速光束的局域空间频率及其在光束设计中的应用

Airy加速光束是近年来备受关注的一种新型无衍射光束. 它所具有的自由加速、无衍射及自恢复特性使其在光学微操纵、非线性光学、 电子加速等诸多领域显示出重要的应用价值. 因此, 如何方便高效地生成加速光束成为近年来的一个热点研究内容. 本文对Airy加速光束复振幅分布的空间振荡特性进行了分析, 建立了利用局域空间频率描述其加速特性的理论. 提出了利用零点坐标计算加速光束局域空间频率的方法, 通过非线性拟合给出了可以精确描述Airy光束局域空间频率的解析公式; 确定了加速光束的局域空间频率函数与加速轨迹之间的定量关系, 给出了由给定加速轨迹计算相应的局域空间频率以及加速光束的纯相位函数的一种简单计算方法. 将上述分析结果用于设计产生具有给定加速轨迹的加速光束所需的相位函数, 成功求出了能够产生圆弧形加速轨迹的新型加速光束的纯相位函数的解析表达式. 基于该相位函数设计的纯相位衍射光学元件的模拟衍射结果证明了上述方法的可行性. 关键词： 衍射光学 加速光束 局域空间频率

Local spatial frequency of Airy accelerating beams and its applications in the beam design

Airy accelerating beams have aroused a great deal of interest because of their non-diffracting and self-accelerating properties, which have many potential applications such as in optical micromanipulations, nonlinear optics and vacuum electron acceleration. A key issue in research of the acceleration beam and its applications is how to generate this specific type of beams with high energy efficiency. In this paper, the spatial oscillation properties of the complex amplitude of an accelerating beam are analyzed and a theory describing the accelerating properties of the beam based on its local spatial frequency is proposed. The local spatial frequency of a general Airy beam is calculated through the zero-point coordinates of the Airy function, and an analytical formula accurately describing the local spatial frequency distribution is given. The relationship between the local spatial frequency and the accelerating trajectory of the beam is also given, based on which a simple algorithm for finding the pure-phase expression of an acceleration beam from its given accelerating trajectory is presented. Finally an analytical expression of the pure-phase function of an acceleration beam for generating a circle-arced trajectory is found out, based on which a pure-phase diffractive optical element is designed and demonstrated successfully.
Keywords： diffractive optics accelerating beam local spatial frequency