A New Near-field Optical Microscope Imaging Numerical Simulation

Photon scanning tunneling microscope (PSTM) is a newly-developed high-resolution optical microscope which can break the resolution limit in optical microscopy. It can detect the sample harmlessly or study the live cells. Thus, it is applied in various fields such as transparent material, biological and medical sciences. Optical-fiber probe is a key component to obtain a true morphology imaging of the sample with high resolusion and efficiency. Since the interactions between the probe and the samples are complicated, the physical model is a multi-body scattering electromagnetical system, a strict theory and analytical expression is very difficult to achieve. Therefore, numerical simulation method occupies an important position in the near-field optics. Among all kinds of the simulation methods, the Finite-Difference Time-Domain (FDTD) method is a simple and effective algorithm and widely applied in the near-field optical numerical simulation.In the PSTM optical imaging, probe as a key factor got widespread concerns. But in the past, our team has noted that the resolution and sensitivity of the near-field imaging for the media-samples and media- probe is poor, even for exciting a small part of probe tip. In this paper, we improved the work by exciting all the probe tips in numerical simulation. The results show that PSTM have a resolution of only 100 nanometers or more in the incident light direction, and even worse in the perpendicular direction. In order to reduce the error of FDTD, we have improved the program, using high performance border algorithm UPML instead of Mur border algorithm. Our team previously had taken note of the work of the probe tip with nano scale metal particles. This kind of probe can improve near-field optical microscope resolution and sensitivity, but it is difficult to apply as the particles may drop. To solve this problem, we have proposed a design of so- called nanostructure thin film, which is media-probe plated by a thin film including nano metal particles, and made a two-dimensional numerical simulation. Based on this simulation, this paper has made a three-dimensional numerical simulation, and further proved that this is a high-resolution, efficient, producible, and invulnerable design to achieve a new near-field optical microscope...