Development and determination of sensitivity of a fiber-optic refractometer based on surface plasmon resonance

A fiber-optic refractive index sensor using the phenomenon of surface plasmon resonance has been developed. A 1 nm layer of chromium and a 50 nm gold film were applied to a section of a standard multimode optical fiber with a partially protected shell. The transmission spectra were measured as a function of the refractive index of the external medium into which the sensor was immersed. When the refractive index of the external medium changed, the minimum in the transmission spectrum caused by the excitation of the surface plasmon-polariton at the boundary between the gold film and the analyte shifted. The sensor sensitivity was 1400 nm/RU.