Post-exposure processing and refractive index change in hydrogen-loaded/annealed fiber grating

Refractive index change induced by post-exposing in annealed and unannealed fiber Bragg grating are investigated in theory and experiment. The relationship between grating index change, initial refractive index distribution and post-exposure are analyzed based on the two-step process photosensitive theory to build up the mathematical models of the refractive mean index and the refractive index modulation change. With 193 nm UV laser post-exposure processing, the evolutions of resonant wavelength and reflectivity are demonstrated and the kinetics of refractive mean index and refractive index modulation are discussed.