A dual layer material coated long-period grating fiber ultraviolet sensor

A high-sensitivity assembled long-period grating fiber (A-LPFG) ultraviolet sensor based on double-layer material film (equivalent refractive index theory) is proposed and validated. This sensor is composed of A-LPFG coated with zinc oxide (ZnO) and propylene glycol film. Among them, the propylene glycol wrapped around the outer layer enhances the response of the sensor to the external environment base on the theory of equivalent refractive index (ERI). Moreover, due to the generation of photogenerated carriers, ultraviolet (UV) sensitivity of A-LPFG coated with ZnO film is significantly improved. The experimental results show that the designed ultraviolet long period fiber grating (UV-LPFG) has a sensitivity of -1.212 nm/(mW/cm2) for UV sensing, with response times of 0.24 s (rise time) and 0.48 s (decay time). In addition, this sensor also has advantages such as high sensitivity, low cost, and good practicality, demonstrating excellent performance characteristics.