On-chip superfocusing of surface plasmon using metal-coat tapered optical fiber pairs with nano-gap structures

Surface plasmons are coupling waves of electron and electromagnetic field at interfaces of metal and dielectrics or metallic nanostructures and localize at the boundary with nanoscale distribution. So, by using surface plasmons, one can construct integrated optical systems to overcome the diffraction limit of light. Recently, a special electromagnetic mode, called superfocusing modes, is important in this research area, owing to high field concentration effect due to increasing of wavenumber of surface plasmons. Metal-coat tapered optical fibers are commonly used for the probes of near-field microscopy and are suitable for fabrication of these superfocusing devices. Furthermore, when these probes are arranged face to face with nano-scale gap, the electric fields in nano-gap also can be enhanced. In this presentation, we show the fabrication processes and numerical analysis of these metal cone structures consist of tapered optical fiber pairs on chip.