Bimetal coated optical fiber sensors based on surface plasmon resonance induced change in birefringence and intensity

We present a surface plasmon resonance (SPR) based multimode fiber sensor with non-golden bimetallic coating. Our detection scheme used, which is capable of measuring the combined effects of SPR-induced birefringence and intensity changes, supported the minimum resolvable refractive index (RI) of 5.8 × 10−6 RIU with the operating RI range of 0.05 to be experimentally obtained at a single wavelength (632.8 nm) without non-spectroscopic techniques. The asymmetric profile of the thickness of the bimetal coating on the fiber core together with the inherent range of incidence angle for multimode propagation also contributed to the wide operating range. The SPR fiber device with the detection scheme demonstrated will be likely to be developed as a real-time label-free and highly sensitive diagnostic device of a wide operating range for biomedical and biochemical applications in a portable format.