Fabrication of plasmonic microcavities on fiber end-facets for high-Q biosensors by transferring the nanoslit arrays from a silicon template

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Surface plasmon resonance (SPR) sensors on fiber end-facets have been paid much attention due to the ultrahigh quality factor (Q) and the figure of merit (FOM), but their scalable and low-cost fabrication remains challenging. Herein, we present a high-efficiency, reproducible fabrication method using a silicon template transfer technique to realize high-performance SPR microcavities with nanoslit-arrays on single-mode fiber end-facets. Benefiting from mature silicon-based lithography and dry etching techniques, the nanoslit-arrays with nearly vertical sidewalls are fabricated sophisticatedly, which effectively suppress radiation loss while improving resonance Q. The fabricated sensor shows a refractive index sensitivity of 532 nm/RIU, an experimental Q-factor of 142, and a FOM of 91RIU −1 , representing a ∼40% performance improvement over conventional direct metal patterning. We further implement label-free biosensing experiments to validate the practical performance of the optimized devices, including dynamic real-time monitoring of bovine serum albumin (BSA) physical adsorption with concentration gradients from 100ngmL −1 −10µgmL −1 . The biosensing results exhibit an ultralow peak-to-peak wavelength shift noise of 2 pm and a sensitive response to trace biomolecular adsorption. The proposed silicon-template stripping transfer method also enables reproducible fabrication to improve manufacturing efficiency and reduce production cost.