Refractive Index Sensitivity Characterization of Tilted Fiber Bragg Grating Based Surface Plasmon Resonance Sensor

We have systematically investigated the refractive index (RI) sensing characterization of tilted fiber Bragg grating (TFBG) based surface plasmon resonance (SPR) sensors in terms of period and tilt angle of grating. The numerical analysis has revealed that the RI sensitivity of TFBG-SPR is linearly proportional to the grating period, and slightly improved with increasing the tilt angle of grating. Under the same normal grating period, the TFBG-SPR sensors with different tilt angles have the different cladding mode order range, which is responding to the different sensing ranges. Furthermore, we have fabricated the TFBG-SPR sensors with different periods and different tilt angles (5 degrees, 7 degrees, 10 degrees, 12 degrees, and 15 degrees). Experimental results show that the larger normal grating period of TFBG is, the higher RI sensitivity of the SPR sensor is, in which the 10 degrees TFBG-SPR sensors with the normal grating period of 529.37 nm, 680.20 nm have the RI sensitivity of 547.6 nm/RIU, 723.6 nm/RIU, respectively. And the TFBG-SPR sensors with different tilt angles slightly affect the RI sensitivity, but the sensors with different tilt angles have different sensing ranges, in which the RI sensitivity of TFBG-SPR sensors with the tilt angle of 7 degrees, 10 degrees, 12 degrees are 545.5 nm/RIU, 547.6 nm/RIU, 549.1 nm/RIU in the RI range of 1.38-1.42,1.33-1.40,1.33-1.37 respectively. Finally, we have discussed the sensing resolution of TFBG-SPR sensor which the larger tilt angle and longer period could worsen the sensing resolution of TFBG-SPR sensor.