Ultrasensitive long-period gratings sensor works near dispersion turning point and mode transition region by optimally designing a photonic crystal fiber

摘要

A novel and ultrasensitive long-period gratings (LPGs) sensor based on photonic crystal fiber (PCF) has been proposed and theoretically investigated. The surrounding refractive index (SRI) sensitivity can be improved enormously by optimizing structure parameters of PCF to ensure LPGs work near dispersion turning point (DTP). Based on this, mode transition (MT) has been also designed and realized in LPGs based on PCF for the first time to further explore the theoretical limit of sensitivity. The simulation results illustrated that the optimized SRI sensitivity is 67,600 nm/RIU in low RI measurement region (1.334-1.344), which is much higher than that of other reported LPGs sensor based on PCF in previous literatures. The competitive advantages make the proposed sensor has a great application prospect in biosensing field, such as biomolecules detection and label-free immune sensing.