Modified chemical vapor deposition and characterization of rare earth ions in heavy metal-doped silica glasses

Fiber optic telecommunication was revolutionized with the introduction of the erbium-doped fiber amplifier (EDFA), operating in the 1.55 mum window. Other rare earths have been investigated for possible operation at 1.3 mum, the wavelength of zero dispersion in silica, but the efficiencies of these devices are typically too low in silicate glasses. Some rare earth ions exhibit higher efficiencies in non-oxide glasses, but the physical properties of these glasses render them inadequate for fiber optic networks. To create a usable device, a rare earth must have a local environment that yields higher efficiencies while residing in a glass host that has the physical properties of silica.; The work conducted in this thesis was designed to explore the possibilities of altering the local environment of the Nd3+ ion while still maintaining a silica glass host. The modified chemical vapor deposition (MCVD) process was utilized in this research due to its flexibility of adding dopants in a homogeneous manner.; The three glass host systems that were explored in this thesis were: Ta2O5-SiO2, HfO2-SiO2, and La2O3-SiO2. The precursors for each of the three modifiers were delivered in vapor form to the reaction zone of the MCVD process by either the chelate delivery method or the injection tube dopant chamber (ITDC) delivery method.; Refractive index, optical absorption, fluorescence emission, and fluorescence lifetime were investigated. The local environment of Nd3+ was inferred based on the analysis of the fluorescence emission spectra. Average photon energy for a given emission was used as a metric to describe both the shape and the position of a fluorescence emission spectrum by a single number. This value clearly showed a correlation between modifier content and fluorescence emission. Neodymium ions preferentially associate with heavy metal ions that most similarly coordinate with oxygen. This preferential pairing was seen based on the aforementioned correlation between modifier content and average photon energy for each modifier system. The work completed in this research provides insight for the possibility of active silica-based optical devices that operate at telecommunication windows other than 1.55 mum.