We experimentally studied the influence of different constructional parameters on the performance of surface plasmon resonance (SPR) sensors based on a commercially available polymer step-index multimode fiber. For the first time, to the best of our knowledge, we experimentally investigated the influence of polishing depth on the characteristics of SPR sensors based on a straight multimode fiber. We also examined the impact of sensing length on the spectral position and strength of the SPR in side-polished straight fibers. To clarify literature contradictions concerning the effect of fiber bending on SPR, we experimentally investigated the performance of U-bent SPR sensing probes based on multimode fibers. We have shown that the SPR can be significantly amplified by bending the polymer fiber with stripped cladding. We also demonstrated that the side-polishing of U-bent sensing probes has little impact on their performance.
For the first time to our knowledge, we report a successful fabrication of surface plasmon resonance (SPR) sensors in a specially developed single-mode birefringent polymer D-shape fiber with a core made of PMMA/PS copolymer. A small distance between the core and the cladding boundary allows to deposit a gold layer directly onto the flat fiber surface, which significantly simplifies the sensors fabrication process. The developed SPR sensor exhibits a sensitivity of 2765 nm RIU−1 for the refractive index of external medium equal to 1.410, which is similar to the sensitivity of the SPR sensors based on conventional side-polished single-mode silica fibers. Using the finite element method, we also numerically studied the sensor performance. The sensor characteristics obtained in the simulations are in a relatively good agreement with the experimental results.
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