Sensing Characteristics of Long-Period Grating Inscribed in Grapefruit Photonic Crystal Fiber by Femtosecond Laser

Abstract

A novel method for fabricating long period grating in grapefruit photonic crystal fiber (GPCF) is proposed and demonstrated. An 800nm femtosecond laser is adopted to scan a section of GPCF periodically point-by-point, resulting in effective refractive index periodic demodulation. High resonance of ~17dB is obtained with a grating length of 30 mm. The temperature sensitivity of resonant wavelength 0.03 nm/°C is obtained from 20°C to 120 °C. In addition, the relationship between resonant wavelength and surrounding refractive index (SRI), when LPFG immersed in refractive index of solution of different index, is also researched.