Ultrafast laser plasma doping of Er3+-doped hybrid tellurite-silica thin films

It has been a decade since the ultrafast laser plasma doping technique was first developed at The University of Leeds by Gin Jose. The capability of the technology to dope Er3+ ions into amorphous hybrid tellurite-silica glass thin films at the high concentrations required for Er3+-doped waveg- uide amplifiers is unrivalled by other techniques. By avoiding clustering and crystallisation of the rare-earth ions, a long metastable photolumines- cence lifetime of the first excited state required for population inversion is achieved. Despite the superior spectroscopic properties of this material, improvements to film homogeneity, quality and controlled growth rate are required. A fundamental understanding of the ultrafast laser plasma doping technique is lacking and is the aim of this thesis. The process is optimised sequentially, from the femtosecond laser ablation of the rare-earth doped tel- lurite target glass, to the ablation plume constituents to the film formation mechanism on silica substrates. Importantly, film formation in a vacuum is demonstrated for the first time and the sub-micron films are crack-free and highly uniform. Dehydroxylation of the silica surface during process- ing is also shown to eliminate quenching centres that typically reduce the metastable lifetime of Er3+ ions. The demonstration of high quality thin film growth, of the order of 100 nm, and capability to dope any rare-earth ion without a change in processing parameters, will allow for the application of this thin film technology to a variety of optical devices, such as sensors and lasers, alongside Er3+-doped waveguide amplifiers.