Performance investigation of fiber–optic SPR sensor utilizing zinc oxide in phase interrogation scheme

Plasmonic fiber optic sensors have emerged as immensely valuable and versatile optical tools in sensor technology in contemporary scientific and engineering disciplines. The analytical performance of a fiber optic SPR sensor is, in general, studied in wavelength interrogation mode. In the current study, the analytical performance analysis of a fiber optic SPR sensor in phase interrogation scheme is presented, which probes the phase difference arising between TE (s) and TM (p) polarized components of the incident light as they propagate through the fiber optic sensing structure. The sensing probe, for this purpose, involves a silver layer of 40 nm thickness over unclad fiber core followed by zinc oxide (ZnO) layer of variable thickness. The plasmonic behavior of the proposed sensor as well as its phase response are explored with respect to analyte refractive index making use of transfer matrix theory developed for N–layered hierarchical optical media. The maximum value of phase sensitivity achieved for the proposed sensor is 2.828×105 deg/RIU for ZnO thickness of 2 nm and at an analyte refractive index of 1.3711, which is observed to decrease with an increase in ZnO thickness.