Fabrication of Type-II Fiber Bragg Gratings with a 300 NM Period Using Tightly Focused Violet Femtosecond Pulses and the Phase Mask Technique

High-temperature stable Bragg gratings (i.e., Type-II Bragg gratings) with a 300 nm period are fabricated in non-photosensitized silica-based optical fibers using tightly focused violet (400 nm) femtosecond pulses and a phase mask. The Bragg wavelength drift and changes in the transmission of the fiber Bragg gratings are monitored in the course of isothermal annealing performed at 1000°C up to 120 hours.