用准静态电磁场方法研究扫描近场光学显微镜的耦合特性

Study on the Coupling Property of Scanning Near-field Optical Microscopy with the Quasi-static Electromagnetic Field Approach

为了研究扫描近场光学显微镜(SNOM)中探针和粗糙样品表面的耦合相互作用,采用准静态电磁场理论的方法,提出了一种模拟SNOM的理论模型。在该模型中,探针和样品突起由极化偶极子表示,样品平面的诱导极化效应由影像偶极子表示,应用偶极子辐射理论可以得到系统的场方程,通过自洽的方法可以求出任意偶极子位置处的严格解析解。该方法与通过并矢传播子方法得出的结果完全相同,其优点在于实用性和计算的简便性。

In order to study the coupling between the probe tip and the rough sample in scanning near-field optical microscopy (SNOM), a quasi-static electromagnetic field approach is adopted and a theoretical model for SNOM is proposed. In the present model both the optical probe tip and the sample protrusions are represented by polarizable dipole spheres. The induced polarization effects on the sample surface can be replaced by the image dipoles. Applying the radiation theory of the dipole, a set of equations to describe the field distribution at the sites of the probe tip and the sample protrusions have been established. This set of field equations can be solved self-consistently. The results are completely the same as those obtained by means of the dyadic electromagnetic propagator formalism. The principal advantage of this approach lies in its practicality and simplicity in calculation.