Imaging properties of three dimensional aperture near-field scanning optical microscopy and optimized near-field fiber probe designs

A series of finite difference time domain (FDTD) methods for obtaining more insight on the near-field distribution of subwavelength aperture and fiber probes are numerically investigated. The treatment of dispersive materials in a time-domain-dependent fashion is considered. Several significant factors are also considered successively, e.g., the near-field distribution of subwavelength aperture in an infinite aluminum plane with sample interactions, the characteristics between the near-field distribution and the depolarization phenomenon, different types of three-dimensional tip (noncoated and metal-coated) used to illuminate a photosensitive sample and the polarization of an incident electromagnetic field. Moreover, the FDTD designs of two types of improved probe are illustrated and a suggestion for fabricating an optimal probe is given. Our proposed structures will yield useful information and guidelines for designing high-performance near-field probes.