Surface plasmon resonances of a curved hetero-core optical fiber sensor

In this work, a novel characterization of surface plasmon resonance (SPR) is described on using a curved hetero-core optical fiber sensor that can flexibly change the radius of curvature of the sensor probe. It has been found that the decrease in the radius of curvature resulted in a 2.8 fold increase in the SPR (loss) spectrum peak with a decrease in spectral bandwidth by 75% and an additional 9-nm shift in the SPR resonant wavelength, compared with the straight case. To discuss the experimental results, the power distribution in the hetero-core region was investigated by using uncoated hetero-core fibers. It was found that the power distribution was shifted to the critical angle by bending, the discussion of which successfully explained the observed bending effect of SPR.