Tunable fiber-end LSPR sensor based on MXene-modified silver nanobowl arrays.

Localized surface plasmon resonance (LSPR) sensors integrated on optical fiber end-faces hold great potential for miniaturized and real-time refractive index detection. However, most reported designs still exhibit weak field confinement and limited control over the local electromagnetic environment, resulting in moderate sensitivity and poor stability. In this work, we present a fiber-end LSPR sensor based on three-dimensional silver nanobowl arrays (SBAs) that enable tunable near-infrared plasmonic resonances through precisely engineered geometry and interfacial coupling. Through structural and dielectric co-engineering at the metal-air interface, what we believe to be new hybrid electromagnetic modes are excited, leading to redistributed near-field energy and enhanced light-matter coupling. Both simulations and experiments confirm a highly linear spectral response with a maximum sensitivity of 845 nm/RIU, corresponding to an approximate 23% enhancement over unmodified structures. The proposed mechanism offers what is believed to be a new route to modulate plasmonic responses through equivalent refractive index engineering and multi-interface coupling. We further show that moderate ion-beam etching (∼180 nm) achieves an optimal balance between structural uniformity and optical loss. The proposed SBAs fiber probes offer a cost-effective and scalable approach to realizing high-sensitivity and stable fiber-end LSPR sensors.