Gratings, photosensitivity, and poling in silica optical waveguides with 157-nm fluorine laser radiation

The energetic 7.9-eV photons of the F2 laser directly access bandgap states in germanosilicate glasses to drive one-photon processes for inducing strong refractive index changes in silica optical waveguides. In this thesis, the author carried out the first comprehensive F2-laser photosensitivity studies with an aim to assess prospects for shaping useful photonic structures directly inside the germanosilicate waveguides. Both planar waveguides and standard telecommunication fibers were examined.; Large effective index change (>10-3) was induced in both fibers and planar waveguides without any enhancement technique. With the use of hydrogen loading enhancement, asymmetric refractive index profiles were noted by atomic force microscopy and microreflection microscopy, having a peak index change of larger than 0.01 in the fiber core.; The 157-nm laser radiation is effective in rapidly forming long-period gratings in standard fibers. Grating formation is over 250 times faster than that with the 248-nm KrF laser constituting the fastest photosensitivity response ever reported. For planar lightwave circuits (PLCs), the 157-nm laser exposure generate narrow profiles of large index changes (Deltan ∼ 10 -2) that is useful in trimming phase errors and controlling birefringence in frequency domain modulators (FDMs) and interleavers. The large vacuum-ultraviolet-induced birefringence was used to completely compensate the intrinsic birefringence of Deltan ∼ 10-4 in typical PLCs.; With hydrogen soaking, modest 157-nm pre-irradiation (accumulated fluence >3 J/cm2) was found to 'lock-in' a permanent photosensitivity enhancement in the germanosilica, permitting the formation of strong (40 dB) and stable fiber Bragg gratings with 248-nm-KrF laser light. The F2-laser photosensitivity locking was 300-time more effective than with KrF-laser pretreatment. The practical trimming applications in PLCs were demonstrated in PLC interleavers and FDMs.; The 157-nm laser pre-radiation was found to have a modest enhancement on the thermal poling process. Thermal poling on 157-nm and 248-nm pre-treated Er/B ring twin-hole fibers showed a 100% enhancement on the residential electro-optical coefficient (0.2 pm/V) in comparison with untreated fibers. The 3rd -order nonlinearity for the thermal poling was also enhanced by both 157-nm and 248-nm pre-radiation. A 2.7-time increase of the 3rd nonlinearity was observed in both 157-nm pre-treated fibers.; The results of this thesis have potentials applications for laser writing and trimming of telecommunication optical components.