Influence of ions on dynamic response of surface plasmon resonance fiber optic sensor

In this paper, the effects of exposed sensing region length on fiber optic sensor based on surface plasmon resonance (SPR) had been experimentally investigated. The refractive index sensitivity of SPR fiber optic sensor increased with increasing refractive index. Compared to other two counterparts, the sensor with short sensing region length of 5 mm demonstrated the highest refractive index sensitivity. For the change in the same magnitude of refractive index, this sensor of 5 mm sensing region length showed significantly different dynamic response curve when it was exposed to ionic (NaCl solution) and non-ionic (ethanol) solution. This result suggests that ions have dramatic influence on the resonance wavelength of surface plasmon resonance spectrum, due to the interaction of ions with gold film surface. This feature provides a great potential of SPR fiber optic sensor to on-line monitor of flowing solution.