The localized and enhanced optical near-field on the asymmetric metal-coated dielectric probe

摘要

As recent trends of integrated optical circuits shows the features of small size, high speed, and flexible structures are expected by many researchers as well as optical devices manufacturers. Many functional devices utilizing surface plasmon polaritons (SPPs) have been proposed and are expected to play an important role in future of nanometric integrated optical circuit [1–4]. There is difficulty in the coupling of incident light into metallic nanostructures since conventional optics cannot focus a laser beam into a region that is much smaller than about half the wavelength of the light due to the diffraction limit of light. Metal-coated dielectric conical probe supporting SPPs can perform above-mentioned function by significantly enhanced and localized near-fields at the tip [1, 2]. These focusing techniques are often called SPP superfocusing or nanofocusing so far. However the symmetric conical probe can be used only for radially polarized (RP) incident field [5–7]. In the practical applications, the linearly polarized (LP) mode in the thin optical fibre will be used [8]. Unfortunately, the symmetric conical probe is not valid for incident LP beam. In order to use the incident LP beam in the metal-coated dielectric conical probe, we propose the structure of asymmetric shape for SPP nanofocusing.