UV-written devices in rare-earth doped silica-on-silicon grown by FHD
This thesis is concerned with the fabrication of all-UV-written devices in rare-earth doped silica-on-silicon to demonstrate the viability of this versatile single step channel definition process for the production of light sources. The requirements for the glass substrate and the fabrication of waveguiding structures through use of the Flame Hydrolysis Deposition technique are discussed. The development of a process for rare-earth doping of the core layer through the immersion of a partially consolidated soot into a solution containing rare-earth ions is presented. The pre-requisites for direct-UV-writing of channels in a three-layer buried waveguide structure are then considered and results on the physical behaviour of the channels and spectroscopic properties of the rare-earth ions are reported. This study has resulted in the first demonstration of an all-UV-written waveguide laser in silica-on-silicon. Low-loss operation (0.11-0.3 dBcm−1) of a 10mm long channel waveguide laser doped with 1.26wt% of neodymium was demonstrated with efficient lasing action (~ 33% slope efficiency). Erbium, ytterbium and thulium doping have been investigated to allow the production of light sources at other wavelengths. Further optimisation is still required to allow lasing to be achieved. Nevertheless, demonstration of y-splitters and Bragg grating fabrication in the doped material shows the potential of the combined fabrication techniques for the production of DFB laser-arrays for WDM technology. The additional developments required for the production of such devices are also discussed.