Electromagnetic near field induced by surface defects in microstructures

The scanning tunneling optical microscopy(STOM) can provide an extremely efficient way for obtaining local information on the complex structures near the surface with arbitrary profile. Self-consistent integral equation formalism (SCIEF) is one of the favorable approaches to calculate the distribution of the electromagnetic held in the vicinity of mesoscopic and nanometric structural defects because this approach has a benefit to avoid the matching procedure of the boundary conditions of the field at every interface of the sample with complex profiles and different dielectric constants. However, the dyadic Green's function introduced in this approach is usually performed in the wave number space representation and it brings complex and tedious calculations. In this work we calculate the distribution of the electromagnetic near field for two kinds of defects lying in a perfect flat surface, three-dimensional (3D) protrusion and hollow, based on the modified SCIEF in the real-space representation. We treat the coupling between the defects and the extended flat surface in the unretarded approximation-- image method. This treatment is appropriate since the distance between the dipole and the surface is far less than the wavelength of illumination light for mesoscopic and nanometric surface defects. This method greatly simplifies the numerical calculation. We first investigate the relationship between the held pattern and the profile of the object and then study the interference effect between adjacent defects. The simulation results demonstrate that the profile of surface defects with subwavelength size can be well detected by properly polarized illumination light.