Square-Wave Long-Period Fiber Grating Fabricated With Double-Sided Laser-Assisted Wet Etching Technology

This study presents a square-wave double-sided long-period fiber grating sensor that was fabricated using pattern inscription by laser-assisted etching with a KrF 248-nm excimer and an aqueous solution of acid. We investigated the relationship between grating depth and the etching rate of the excimer laser-irradiated fused silica. The novelty of this sensor lies in the square-wave period grating structure created by a different etching rate on the surface of the optical fiber during the laser-assisted wet etching process and the designed period of two metal masks. We also conducted experiments that demonstrated the sensitivity of the square-wave double-sided long-period fiber grating sensor to temperature. The results showed that the average resonant wavelength/temperature ratio of the sensor was 0.054 nm/°C, while the transmission loss/temperature ratio was 0.038 dB/°C.