照明模式SNOM中样品对近场光场分布的影响

Effects of the Samples on the Near-field Electromagnetic Field Distributions in Illumination-mode SNOM′s

在同时考虑样品的形貌及材料光学参量和入射光偏振模式的情况下,利用基于边界元方法编写的二维矢量电磁场计算程序,对工作在照明模式下的扫描近场光学显微镜(Scanning Near-field Optical Microscope,SNOM)的近场矢量电磁场分布进行了数值计算模拟研究.结果表明,在没有表面形貌特征时,探针的光能量透射率随样品材料的折射率和损耗角的增加而增大,而样品表面光斑尺寸受折射率和损耗角的影响很小;对有形貌特征的探针扫描像研究结果表明,SNOM的分辨率随着样品的折射率和损耗角的增加而提高;对SNOM不同的工作模式的扫描成像信号进行的计算结果表明,恒定间距扫描方式比恒定高度扫描方式对样品表面的细节有较强的分辨能力.

The near-field vector electromagnetic distribution in illumination-mode scanning near field optical microscopes （SNOM） was studied numerically using a two-dimension program based on the boundary element method, taking into consideration of both the sample properties and the polarization of the input light. The numeric results indicated, that in the case of topography free samples, the power transmission of the optical probe was increased with the increase of the permittivity and the loss angle of the sample material, and that the spot size was hardly effected. However, in the case of topographic samples,the resolution of the SNOM was increased with the increasing of the permittivity and the loss angle of the sample material. Comparison of two operating modes of SNOM indicated that the constant distance image had a higher resolution for the local change of the sample topography than the constant height image.