硬X射线光子筛波导效应研究

The waveguide effect of hard X-ray photon sieves

基于快速傅里叶变换光束传播法,研究了硬X射线光子筛中高高宽比金属结构的波导效应,确定了硬X射线光子筛的物理边界条件,采用角谱法计算了硬X射线光子筛的点扩展函数,并分析了吸收体厚度对聚焦性能的影响.研究结果表明波导效应一定程度上有利于抑制光子筛高级衍射的产生,提高聚焦性能.在同样的特征尺寸下,硬X射线光子筛的空间分辨率优于菲涅尔波带片,其缺点是衍射效率的下降.吸收体厚度的提高有利于提高光子筛的聚焦性能和衍射效率,但是相应的纳米加工工艺难度会增加.

In this work,the waveguide effect inside the high high-aspect-ratio metal structure of hard X-ray photon sieves is studied based on fast fourier transform beam propagation method （FFT-BPM）. After the physical boundary condition immediately downstream of hard X-ray photon sieves is determined by FFT-BPM, the angular spectrum method is used to calculate the point spread function,and the absorber thickness impact on the focusing performance is analyzed. The results show that the waveguide effect can suppress the emergence of the high order diffraction of hard X-ray photon sieves to some extent,thus improve its focusing performance.Under the same feature size conditions, the spatial resolution of hard X-ray photon sieves is better than that of Fresnel zone plates,with the drawback of lower diffraction efficiency.With the absorber thickness increasing, both the focusing performance and diffraction efficiency of photon sieves will improve, but the difficulty of the corresponding nanofabrication process will also increase.