Abstract
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.
Highlights
Surface plasmon resonance (SPR) sensors utilize surface plasmon polaritons (SPPs) that can be excited through an array of subwavelength metallic nanostructures[19,20,21,22]
Given the band structure profiles of the two 1D gratings (Fig. 2b), for a 2D rectangular Au grating with Px of 1030 nm and Py of 1230 nm, it is conceivable that there exists two resonance modes that are spatially separated in the C + L band: Band 1 in the solution side and Band 4 in the silica side
We developed a lab-on-fiber multiparameter nanoprobe for simultaneous sensing of solution refractive index and temperature
Summary
SPR sensors utilize surface plasmon polaritons (SPPs) that can be excited through an array of subwavelength metallic nanostructures (e.g., holes, patches, and gratings)[19,20,21,22]. Most on-fiber SPR sensors are based on the measurement of refractive index change induced resonance wavelength shift, which is highly sensitive to the surface characteristics. High-Q SPR sensors were demonstrated on single-mode optical fibers by using a plasmonic crystal cavity[28,29] and a distributed-feedback surface plasmon resonator[30] for biochemical sensing and ultrasound sensing. An attractive alternative is an on-fiber multiparameter sensor, which supports multiple SPRs with distinctive responses to the changes of refractive index and temperature. Our group reported a multiparameter sensor that utilized the combined response from a single SPR and a plasmonic interferometer obtained with an Au nanohole array fabricated on a single-mode optical fiber[31]. The small mode area and broad range of incident angles of the fiber guided mode resulted in a relatively low-Q (~50) SPR, which limited the accuracy of the SPR wavelength measurement
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