Bragg grating inscription in BDK-doped PMMA optical fiber using femtosecond laser point-by-point technique

In this work, we reported 2-mm-long fiber Bragg gratings (FBGs) in benzyl dimethyl ketal (BDK)-doped poly(methyl methacrylate) (PMMA) optical fibers by means of a 520 nm femtosecond laser and point-by-point FBG inscription technique. The highest reflectivity of ~99% is obtained with a pulse energy of 11.2 nJ, showing a large refractive index modulation amplitude of 7.2×10^-4 .