偏振激光照明对多层薄膜结构成像对比度影响

Effect of polarized laser illumination on imaging contrast of multilayer thin film structure

光学多层干涉断层扫描技术(Optical multilayer interference tomography,OMLIT)应用于光电关联显微镜中以实现清晰的光学大视场成像,为高分辨率电镜图像提供目标区域标定。为了进一步提升成像对比度和定位精度,将偏振照明和OMLIT成像技术相结合,提出一种多层薄膜偏振照明的理论模型,使用矩阵传输方法对不同入射角的偏振光在不同材质、厚度的多层薄膜介质间的传播及干涉成像进行了仿真。结果表明,当照明光的电场振荡方向平行于入射面时,能够获得比非偏振光更高的图像对比度。当照明光以62°入射角照射金属银镀层样品表面,成像对比度提升高达138倍。这项工作为偏振照明OMLIT提供了理论基础,为光电融合显微成像技术的发展提供了全新的技术方案。

Optical multilayer interference tomography(OMLIT)is used in correlated light and electron microscopy to image a large field through an optical microscope,providing the navigation of the region of interest for later nanometer-resolution electron microscope imaging.In order to further improve the imaging contrast and positioning accuracy of thin film samples,a theoretical model combining polarization illumination and OMLIT is proposed.This model is written in the matrix formalism and the propagation of polarized light through different layers with various incident angles is simulated.The simulation results show that using the polarized light with an electric field oscillating parallel to the incidence plane(p-polarization)exhibits a much higher imaging contrast than the unpolarized light.Especially when the p-polarized light illuminates on an OMLIT sample,of which the first coating layer is Ag,with an incidence angle of 62°,the imaging contrast can be vastly enhanced by 138 times.The presented model provides a theoretical basis for polarization illumination OMLIT,pathing a new technical way for the development of the correlated light and electron microscopy technique.