近场显微干涉成像中的探测角度和偏振问题研究

用偶极子耦合系统来模拟近场干涉测量中的探针样品关系,并利用各电场分量之间的组合方程组精确计算出其可能探测到的强度和相位像。结果显示,近场干涉所测量到的近场像的分辨力和探测器的方位及参考光的偏振方向之间有较强的依赖关系,随着探测器位置不同或者参考光偏振方向的变化,同一样品在同一照明条件下所得到的图像也会发生明显的改变。在倏逝波照明的情况下,近场像的精确度随着探测器相对于样品视角的增大而改善,且在不同偏振方向的近场像中,只有偏振方向垂直于样品表面的像能真实反映样品的细节分布,且同时具有足够的强度分布。

Detection-Angle and Polarization Dependences of the Interferometric Imaging with Near-Field Scanning Microscopy

The interaction between the specimen and the scanning probe in the near-field interferometry was modeled with a coupled point-dipole system, and a set of equations of different electric field components were used to calculate the intensity and phase images of the specimen. It was found that, the resolution of the near-field images was strongly dependent on both the polarization direction of the reference light and the position of the far-field detector and vice versa. For a specimen under given illumination, its near-field images changed remarkably with the slight adjustment in the detector position or the polarization of the reference light. In the case of evanescent illumination, the resolution of differently polarized images increased with the view angle of the detector to the specimen, and highly accurate images could be realized only when the detector was placed at a large enough view angle. Among the images of differently polarized components, only the image polarized normally to the specimen surface indicated the specimen in details with enough intensity.