Fiber optic surface plasmon resonance sensor with a Bragg grating

Abstract

We report a new optical sensor based on excitation of a surface plasmon (SP) in an optical fiber Bragg grating (FBG) structure. The sensing device consists of a side-polished single-mode optical fiber with a Bragg grating written into a fiber core and a thin gold overlayer supporting SP. If a coupling between a guided mode of the optical fiber and a SP mode is established, any change in the refractive index of analyte affects propagation constant of the fiber mode producing a change in the amount of light reflected by the FBG. A laboratory prototype of the sensor has been developed and its potential for refractometry has been examined. It has been demonstrated that the sensor's sensitivity to refractive index is as high as 750 dB/RIU (Refractive Index Unit)