Multi-Channel SPR Measurement by Scanning a Fiber-Optic Probe in a Gold-Coated Silica Sleeve

Fiber-optic surface plasmon resonance (SPR) sensing has gained widespread recognition as a promising tool for biochemical analysis, yet achieving multiplexing with this technology has remained a challenge. Here, we propose and demonstrate a new fiber-optic sensing approach capable of conducting multi-channel SPR measurements. The device comprises a hetero-core optical fiber probe inserted into a gold-coated silica capillary prefilled with refractive index (RI) matching oil. The cladding modes in the hetero-core optical fiber probe extend into the silica capillary and excite the SPR effect in the gold nanofilm on the outer surface. By adjusting the position of the fiber probe inside the capillary, surface RI at different points can be sequentially measured. A five-channel sensor was experimentally constructed, showing sensitivities of ∼ 2250 nm/RIU in the RI range of 1.3327-1.3665 and inter-channel error below 1.5%. This sensing approach presents a new avenue for multi-channel biochemical sensing and demonstrates significant potential for high throughput disease diagnosis and molecular screening.