Micro-Lab on Tip: High-Performance Dual-Channel Surface Plasmon Resonance Sensor Integrated on Fiber-Optic End Facet

It is a challenging and valuable work to realize the simultaneous sensing of two or more parameters at the end of optical fiber. In this paper, we implemented an ultra compact dual-channel surface plasmon resonance (SPR) sensor on fiber-optic end facet. A dual-layer polymer microcap based on different refractive index (RI) films was used to segment a single Cu/TiO2 coated micro-cone on single mode fiber (SMF) end facet for producing a sensing spectrum with two separated SPR dips. The SPR dip (channel-II) generated by Polydimethylsiloxane (PDMS) microcap can reach high sensitivity temperature measurement of 2.935 nm/°C in the range of 30–70 °C, and the SPR dip (channel-I) generated by polyvinyl alcohol (PVA) microcap can achieve high sensitivity humidity measurement of 1.08 nm/%RH in the range of 20%RH-70%RH. Finally, the simultaneous detection of humidity and temperature can be realized by the matrix established by channel-I and channel-II. This is a simple, effective and reproducible micro laboratory on optical fiber end facet for dual parameter sensing.