Pulsed laser deposition and characterisation of rare earth doped glass-polymer optical materials

Tellurite glass is well known for its excellent optical properties in the application of optical fiber and planar waveguide devices, particularly for optical amplifiers. This
thesis is focused on the design, fabrication and characterisation of tellurite glass in both bulk and thin films (glass, glass and polymer thin films) used as optical
materials. It consists of four major parts, including the fabrication and characterisation of rare earth doped tungsten lanthanum modified tellurite (TWL) glasses, TWL glass thin films, glass and polymer composite thin films as well as the fabrication of channel waveguide structures on the surface of thin films.

One of the main objectives of this research is to engineer rare earth doped glass and polymer composite thin films using pulsed laser deposition (PLD). Thin films are the
main form of the prototype for planar devices. Two dissimilar materials with comparable refractive indices have been deposited alternatively to obtain a periodic
layer by layer structures using PLD. These two materials, namely, phosphate modified tellurite (PT) glass and siloxane polymer (PDMS), are both excellent optical materials with low propagation loss at the optical communication window. One of the merits of PT-polymer composite is that it could combine the advantages
of the good characteristics of both PT glass and siloxane polymer as optical materials. The success of this fabrication opens a door to engineering composite thin films
using a simple and low cost technique with a precise control.

The second objective of this research is to fabricate rare earth doped tungsten and lanthanum modified tellurite (TWL) glass thin films on polymer coated silica to produce another kind of glass-polymer composite. The TWL glass has a
significantly different refractive index to siloxane polymer. It is not suitable for fabricating multilayer thin films. Here, dual layer composite thin films were
produced by depositing rare earth doped TWL glass onto polymer coated silica substrate using PLD.

Furthermore, to optimize the composition of rare earth doped TWL glass and the deposition parameters of the fabrication of TWL glass thin films, a series of rare earth doped TWL glasses and series of TWL glass thin films on silica were produced and characterized in detail.

Finally, to study the feasibility of making optical devices on these thin films, reactive ion etching (RIE) and fs laser micromaching techniques were utilized to a create
ridge waveguide which is the primary structure of optical amplifiers. The SEM images of the ridge waveguide and depths of the waveguides were studied. In addition, the mode profile and propagation loss of the ridge waveguide obtained using fs laser micromachining were investigated.