Analysis of surface plasmon resonance based bimetal coated tapered fiber optic sensor with enhanced sensitivity through radially polarized light

• A proposal of bimetallic taper fiber sensor with radially polarized light.
• Enhanced sensitivity to detect the refractive index variation with SPR.
• With radial polarization sensitivity enhanced 10 times compared to symmetrical one.
• Sensitivity has been investigated with wavelength and intensity interrogation.
• With red shift temperature effect on proposed structure has also been represented.

The presented proposal of surface plasmon resonance (SPR) configuration with tapered fiber structure and radially polarized light beam is a new and different analysis towards the sensitivity enhancement in the field of SPR based fiber optic sensors. Here the taper waist region of optical fiber having diameter around 330 μm is deposited with 40 nm thin Ag layer, 10 nm thin Au layer and the sensing layer with refractive index 1.333–1.353 respectively for achieving the bimetal coated taper fiber optic sensor with SPR configuration. The cylindrical symmetry and special radial field distribution of radially polarized light make its more interesting SPR study and leads to the enhanced excitation of surface plasmon wave. This results 10 times better sensitivity of fiber optic sensor output response as compared to p-polarized light beam with wavelength interrogation technique and 2.307 times better sensitivity with intensity interrogation technique. Also including the temperature effect in proposed taper bimetallic structure, this sensitivity analysis provides an evidence, for exploring a new idea towards the enhanced excitation of SPR which expedites the new avenues in the field of sensor applications with radially polarized light.