Lab-on-Fiber Nanoprobe with Dual High-Q Rayleigh Anomaly-Surface Plasmon Polariton Resonances for Multiparameter Sensing.

Surface plasmon resonance (SPR) based sensing is an attractive approach for realizing lab-on-fiber nanoprobes. However, simultaneous measurement of multiple parameters (e.g., refractive index and temperature) with SPR-based nanoprobes, although highly desirable, is challenging. We report a lab-on-fiber nanoprobe with dual high-Q Rayleigh anomaly (RA)-surface plasmon polariton (SPP) resonances for multiparameter sensing. To achieve high-Q RA-SPP resonance the nanoprobe employs a plasmonic crystal cavity enhanced by distributed Bragg reflector (DBR) gratings on the end-face of a single-mode optical fiber. By tailoring the grating periods of the plasmonic crystal cavity and DBRs, two spatially separated high-Q RA-SPP resonance modes are designed within a 50 nm spectral range in C + L band. The fabricated nanoprobe demonstrates two RA-SPP resonances near 1550 nm with high Q-factors up to 198. These two high-Q resonances are further showed to exhibit distinctive responses to the changes of refractive index and temperature, which enables simultaneous measurements of both parameters. The proposed lab-on-fiber nanoprobes will pave the way for realizing compact multiparameter sensing solutions compatible with optical communication infrastructures.