Study on the near-field optical properties of metal-clad cutting-off fiber probe with a sub-wavelength aperture

This paper studies the distributions of the near field and its energy flux density of fiber probes using Finite Integration Method (FIM). The principle and advantage of FIM are discussed. Two probes consisted of metal-clad cutting-off fibers with different aperture size were computed, and the results indicate that there is a standing wave exists along axial of the optical fiber, and an evanescent wave exists outside the optical probe aperture. The field and energy density distributions in near-field region are discussed in detail. A boundary enhancement effect exists at the aperture on the polarization direction of the input light, and it becomes weaker when the aperture size is decreasing. The aperture size is important for both the optical resolution of SNOM and the energy density in the near-field area, which determines interaction of the near-field and the energy transmission efficiency of the probe.