Application of optical fibres with reduced normalized frequency for SPR-based refractometry

We present a numerical analysis of surface plasmon resonance (SPR) excitation in a bent metal-coated single mode optical fibre with a low normalized frequency. It is shown that by choosing a proper combination of fibre parameters, such as bend radius and metal film thickness, a direct energy transfer can occur from the fundamental mode, guided by the fibre core, to the surface plasmon wave excited at the metal layer applied to the fibre cladding. The prospects for precision refractive index measurement based on the proposed configuration are discussed, with the spectral sensitivity and resolution estimated at 70 um/refractive index unit and 3⋅10⁻⁷, respectively.