Superfocusing of surface plasmon polaritons by metal-coated dielectric probe of tilted conical shape.

By the volume integral equation method, the metal-coated dielectric probes of tilted conical shape were investigated for nanofocusing of surface plasmon polaritons (SPPs). We consider the cases of incident radially polarized (RP) and linearly polarized (LP) Gaussian beams and found that the tilted SPP conical probe is valid for both incident linearly and RP beams. Compared to the other asymmetric structures reported so far that are valid for incident LP waves, the structure proposed in this paper is not only simple but also straightforward to obtain the nanofocused localized and enhanced optical field on the tip of incident LP beam.