Bragg Grating Inscription With Low Pulse Energy in Doped Microstructured Polymer Optical Fibers

We demonstrate that fiber Bragg gratings (FBGs) can be written in a doped polymer optical fiber (POF) in a low ultraviolet (UV) pulse energy regime (60 μJ/pulse) using a 248-nm krypton fluoride excimer laser system. The total energy density per inscription necessary to obtain Bragg gratings is between 493.6 and 3825 mJ/cm2, depending on the number of pulses and the pulse energy. The impact of the pulse energy on the growth of the Bragg grating is investigated, and it is shown that the 248-nm light induces a positive refractive index change. This article demonstrates that the FBGs can be obtained in the POFs without high pulse energy (mJ level) at 248-nm wavelength, which reduces maintenance costs. Furthermore, we can consider it as a solution to increase the lifetime of the laser system without high energy still allowing fast and efficient production of the FBGs for sensing applications.