Billy Richards completed a PhD from the University of Leeds in 2008 in near-infrared fibre laser development using tellurium oxide based glass fibres. His research experience includes fabrication and characterisation of a wide range of optical materials such as rare-earth doped glasses for laser and other photonic applications, laser cavity construction, and spectroscopy, resulting in more than 20 journal publications. During his academic career he has worked closely with various industry partners, including a >1 year secondment to Glass Technology Services’ Innovation Team, has been PI and CoI on several collaborative grant-funded projects, and a Marie Curie Fellow working in industry in Italy. Within the EPSRC funded ‘SeaMatics’ project, he is researching the development of micro laser cavities using the thin film gain materials fabricated at the University of Leeds.
Formation of tellurite-modified-silica glass thin films containing rare earth ions using ultrafast laser plasma doping
Billy Richards1*, Artitsupa Boontan1, Eric Kumi Barimah1, Christopher Russell2,
Paul Steenson2 and Gin Jose1
1Applied Photon Science, School of Chemical and Process Engineering, University of Leeds,
Leeds LS2 9JT, UK
Ultrafast pulsed lasers with pulse durations of 40-100 fs are used to deposit rare earth doped tellurite glass onto silica glass substrates in a pulsed laser deposition (PLD) chamber. Under certain conditions, the tellurite glass plasma mixes with the silica glass network producing a thin glass film of tellurite-modified-silica which produces some unique physical, and when doped with rare earth ions, spectroscopic properties. Layers of tellurite-modified-silica glass up to 2 µm thick have been produced with refractive indices of around 1.65, compared to 1.46 and 2.0 for the silica substrate and tellurite target glasses, respectively. Electron microscopy of the thin films shows a sharp and well defined boundary between the modified layer and the pristine substrate, and X-ray spectroscopy (EDX) confirms that the constituent ions of the target glass are uniformly distributed within the substrate silica glass network. Rare earth ions can be doped into these layers in concentrations which are higher than would be possible in pure silica glass without clustering, and Er3+ for example exhibits unusually long 1535 nm fluorescence lifetimes in these thin films. Tm3+ ions have also been doped into these layers, yielding longer wavelength fluorescence, up to around 2000 nm. By codoping Tm3+ and Er3+ ions, broadened fluorescence bands are possible which are of interest for broadband optical amplification. Additionally, codoping with Yb3+ allows efficient excitation using a convenient ~980 nm laser diode source. This technique of producing thin films is also being used to integrate dissimilar materials such as semiconductors, polymers and glass. In this presentation, we will describe the fabrication of rare earth doped tellurite-modified-silica thin films; the physical characterisation of the films including thickness, refractive index and surface roughness; and the optical properties such as transmission and fluorescence.
Figure 1. Fluorescence spectra of Tm3+ doped thin film.
Figure 2a Thickness and figure 2b refractive index map of Tm3+ doped thin film measured using the prism coupling technique at a wavelength of 633 nm.