157-nm radiation-induced Bragg gratings in silica optical waveguides

This thesis reports the first detailed study of Bragg grating writing using 157-nm radiation. The 7.9-eV photon from the 157-nm laser is attractive for inducing strong index changes in germanosilicate and fused silica. Fiber Bragg gratings were written in standard telecom fiber (SMF-28), with index modulation of ∼1.7 x 10-4 in hydrogen-free SMF-28. The gratings have good long-term stability, and sidelobe suppression of 17 dB without apodization. The index modulation improves to ∼6 x 10-4 and Deltan∼1.8 x 10-3 in hydrogen-loaded SMF-28. Bragg gratings were fabricated in pure fused silica holey fiber, yielding Deltan∼1.4 x 10-3 at 90 kJ/cm2 fluence exposure, and offered good cladding mode suppression. Bragg gratings were also written within silica-on-silicon planar waveguides and buried waveguides in fused silica blocks. The results demonstrate an alternate laser source for writing fiber Bragg gratings not requiring photosensitivity enhancement in germanosilicate waveguides, and is practical for writing gratings in pure fused silica holey fiber.