Fiber Bragg grating inscription by high-intensity femtosecond UV laser light: comparison with other existing methods of fabrication

By use of high-intensity (approximate to200 GW/cm(2)) femtosecond 264-nm laser light and a phase mask technique, Bragg grating inscription in a range of different photosensitive and standard telecom fibers (both H-2-free and H-2-loaded) was studied. The dependences of the induced refractive index modulation versus the incident fluence as well as the thermal decay curves were compared with similar dependences for gratings fabricated by other existing methods. It was shown that with high-intensity UV laser irradiation, two-quantum photoreactions occur in the irradiated fiber core, that result in a significant photosensitivity enhancement of the investigated fibers in comparison with conventional low-intensity 248-nm exposure (by 6-128 times, depending on fiber type and irradiation intensity). (C) 2005 Optical Society of America.