Experimental study of high sensitive surface plasmon resonance refractive index sensor based on coreless fiber coated Au film

A high-sensitive Surface Plasmon Resonance (SPR) refractive index sensor based on Coreless Fiber (CF) is presented and experimentally demonstrated in this paper. The refractive index sensor is constructed by using a specific length of metal film coating CF sandwiched with two segments of multimode fibers (MMFs). The metal film is deposited on the surface of the CF by magnetron sputtering technique so as to enhance the detection sensitivity of the refractive index by utilizing SPR effect. A series of experiments are performed to investigate the effects of CF length, coating time and the type of metal film on the sensitivity of CF-SPR refractive index sensor. The resolution, figure of merit (FOM), and experimental repeatability of the sensor are also evaluated in terms of experimental results. The results demonstrate that the sensor achieves a maximum sensitivity of 7166.27 nm/RIU when the refractive indices of the analytes are changed within the range from 1.3331 to 1.3794, which is significantly higher than the sensitivity of most of current reports about the refractive index sensors. Additionally, the maximum FOM can reach 105.39 RIU⁻¹ and the resolution reaches up to 5.16 × 10^-5 RIU. The CF-SPR refractive index sensor has distinguished advantages of high sensitivity, straightforward structure, ease of fabrication and reusability, which has highly potential application in chemical analysis and marine detection.