Research On Spectral Properties Of Tilted Fiber Grating SPR Sensor

Noble metal nanostructures have gained great attention in areas of biosensor and imaging applications, etc. Most of the applications are closely associated with surface plasmon resonance(SPR). The properties of SPR strongly depend on the subtle change of the refractive index of surrounding environment. SPR sensors based on the prism structure have already entered the market, but the disadvantages such as large volume,incapable remote sensing limited its wide utilization. Therefore, the focus is on how to turn it miniaturized or miniaturized. As special short period fiber grating, Tilted Fiber Grating(TFBG) made the core mode coupled into the cladding mode due to its structural characteristics. Furthermore, SPR is excited by the reverse transmission of cladding mode which can be applied as excitation source.In this work, tilted fiber grating were systematically investigated by spectrum properties of surface plasmon resonance sensor based on SPR technology and TFBG, and changes of the TFBG transmitted spectrum with grating angle, grating period, grating length, refractive index of the surrounding medium were calculated by using numerical calculations. Additionally, the variation of SPR spectrum with metal film materials, thickness of the external medium, the refractive index and other parameters were investigated, respectively. Based on TFBG-SPR design concept, the parameters of TFBG-SPR sensor structure were optimized. Through comprehensive analysis, gold was determined as metal film material, the film thickness of 50 nm, dip angle of 7 ° was selected as the best sensitivity and resolution of inclined optical tilted fiber grating sensing element. Moreover, gold film layer thickness of 50 nm was coated on the surface of TFBG plating using the sputtering coating method, made into TFBG- SPR sensor, and carried on the experimental study. The experimental results show that the extinction spectrum is red shifted with the increase of the refractive index of the surrounding medium. The relationship between peak wavelength and the refractive index are substantially linear. It is also found that TFBG-SPR sensor and the refractive index vary linearly and the sensor has higher sensitivity, which verified the practical application of this sensor.