Highly sensitive long range surface plasmon based liquid sensor by shining the radially polarized light in bimetallic taper fiber structure

Abstract

A new approach towards the enhancement of sensitivity in fiber optic liquid sensor is proposed, designed and simulated using the long range surface plasmon resonance technique shining the radially polarized light in bimetallic fiber structure, which comprises a fiber core coated with 40 nm and 10 nm thin Ag and Au layer respectively. The radially outward field distribution of the radially polarized light enables the multiple point plasmonic interaction on the whole fiber periphery which enhances the sensitivity as well as the dynamic range of refractive index sensing through the proposed sensor. A 13 times and 25 times better sensitivity has been estimated using NaCl and KCl solution as compared with the existing articles till date using p-polarized light. Minimum measurable concentration is 0.5 g/l and 1 g/l for NaCl and KCl solutions for a minimum change in output power of 30.04 μW and 25.60 μW respectively using InGaAs detector. With enhanced sensitivity and higher dynamic range of refractive index, this new idea explores the new avenues in the field of fibre optic liquid sensing applications.