Surface plasmon polaritons in standard optical fibres with a metallised cladding

A numerical study is presented of a novel approach to fibre optic SPR-sensor development for biosensing applications. The proposed technique is based on a standard SMF-28 type bent single-mode optical fibre with a thin metal film applied to its optical cladding. It was shown that by adjusting the curvature radius and the metal film thickness, one can achieve effective coupling between the fundamental mode of the fibre and the surface plasmon mode supported by the metal/surrounding medium interface through the meditation of whispering gallery modes propagating along the bent inner surface of the fibre cladding. This effect is demonstrated to enable refractometric measurements, both in the wavelength and in the intensity-modulated regimes, with a resolution of up to 10-8 RIU. The use of standard noise reduction techniques for intensity-modulated optical signals promises further increase in accuracy.