Focusing Characteristics Optimization of Composite Near-Field Fiber Probe Based on Surface Plasmon

In this paper, a surface plasmon probe with the combination of aperture and scattering is presented. On the basis of a commercial AFM (Atomic Force Microscope) probe, a composite probe based on the combination of surface plasmon enhancement and scattering probe focusing was formed by coating SiO2 probe and etching a single ring. The structure of the probe was optimized, in order to achieve larger enhancement of the light field. Furthermore, the combination of aperture SNOM (Scanning Near-field Optical Microscope) illumination can greatly suppress background noise and achieve higher signal-to-noise ratio. By these two technologies, interference optical system and phase-locked technology can be avoided, thus simplifying the design of SNOM instruments. The finite-difference time-domain method is utilized to simulate and calculate the field distribution of the focusing spot and optimize the microstructure of the excited surface plasmon, which provides a strong theoretical support for the probe fabrication.