Expanding the parameter space in optimising femtosecond laser written waveguides for photonics devices

Conferencia inviatada. ICOOPMA, 2014 Workshop and Young Scientists Forum, Leeds, UK, Sunday 27th July – Friday 1st August 2014. Published in Journal of Physics: Conference Series (JPCS).The major aim that was put forward when fs-laser writing was first introduced, almost two decades ago, was producing 3-D photonic structures. This aim has been often limited since the parameter space domain for optimising laser written waveguides was mostly restricted to the way laser energy is coupled inside a dielectric (i.e. laser and processing parameters). This is the first time optimization is achieved by using the target material constituents via controllable local compositional changes. Henceforth we try to put forward and explanation of the process in a way that the device performance can be enhanced. We have shown the feasibility of producing efficient optical waveguides via laser-induced ion-migration in two different glasses distinctive for their special optical properties for the fabrication of photonic devices: a phosphate and a tellurite glass. In both cases two adjacent high and low refractive index regions with different compositions are observed in the laser written waveguides. The local compositional changes, assessed by electron beam probing, show the general trend of multivalent ions (La3+, Al3+, Yb3+, Er3+, Ce3+, Zn2+, Si2+,4+, Te4+, 6+) migrating towards the densified zone while monovalent ions (K+, Na+, P+,3+) are found enriching the low refractive index zones. The migration of multivalent ions is still unexplained but the monovalent ion migration could be explained with the theory of ionic diffusion in glasses where monovalent ions diffuse towards the defect rich zones via vacancy/interstitial/defect transport.Peer Reviewe