Strong photosensitivity responses with the use of above-bandgap 157-nm F2-laser radiation are reported for standard germanosilicate fiber. A large 1.3 × 10-3 effective index change at 1.55 µm was inferred by trimming strong and weak Bragg gratings in hydrogen-free fiber. The F2-laser fluence-processing window of < 50~ mJ/cm2 is much lower than with traditional ultraviolet (UV) lasers. For hydrogen-soaked fiber, highly asymmetric refractive-index profiles were noted by atomic force microscopy and microreflection microscopy, yielding a peak index change of > 0.01 across a small 1-µm penetration depth at the fiber core. The index asymmetry appears to underlie the large > 5 × 10-5 value of laser-induced birefringence.
© 2003 IEEE
Kevin P. Chen, Peter R. Herman, Rod Taylor, and Cyril Hnatovsky, "Vacuum-Ultraviolet Laser-Induced Refractive-Index Change and Birefringence in Standard Optical Fibers," J. Lightwave Technol. 21, 1969- (2003)