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Deposition and modelling of rare-earth doped optical films

Massarek, Ilana; (1994) Deposition and modelling of rare-earth doped optical films. Doctoral thesis (Ph.D.), University College London (United Kingdom). Green open access

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For integration within optical circuits, active devices should ideally be kept as short as possible. As the gain of a device is related to its length and the concentration of active ions, it is necessary for short active devices to contain high levels of ion dopants. The experimental aim of the work presented in this thesis was to determine whether highly erbium-doped silicate glass (Er3+-SiO2) can be fabricated with suitable characteristics to produce planar active devices. The performance of rare-earth doped optical amplifiers was analysed theoretically. In highly doped materials, the optical gain is affected by ion-ion interactions. By solving the rate equations for the levels involved in radiative transitions in the model, the material gain was predicted as a function of the pump power and Er concentration. The negative effects of ion-ion interactions on gain can be overcome by careful design of the waveguide geometry and refractive index step. In particular, the dependence on Er3+ concentration of threshold pump power and amplifier gain are discussed. Plasma enhanced chemical vapour deposition (PECVD) was used to deposit the thin films. PECVD is a non-equilibrium low temperature deposition process. The deposition conditions of aluminium oxide, silicon dioxide, and erbium oxide were studied. By analysing the chemical composition, refractive index, deposition rate, and uniformity of the films, the process conditions were optimised. The silicon dioxide and erbium oxide processes were combined to fabricate Er3+-doped silicate planar waveguides. The Er doping was achieved using Er(thd)3, a volatile organic precursor. Waveguides with a dopant concentration of 1020-1022 ion/cm 3 showed the typical fluorescence spectra of the Er 3+-ion and had a radiative lifetime of 9ms before annealing and 2-3ms after annealing and for high pump powers.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: Deposition and modelling of rare-earth doped optical films
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: (UMI)AAI10045657; Applied sciences; Optical circuits; Rare-earth doped optical films
URI: https://discovery.ucl.ac.uk/id/eprint/10099560
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