Electron-beam modification of silica for integrated optics

García Blanco, Sonia (2003) Electron-beam modification of silica for integrated optics. PhD thesis, University of Glasgow.

Abstract

Germanium-doped silica deposited by flame-hydrolysis deposition (FHD) is one of the materials most widely used for the fabrication of passive optical circuits for the telecommunication and bio-sensors industries. The development of novel fabrication techniques that reduce the number of processing steps while producing high-quality waveguides with tailored characteristics is desired. Electron-beam irradiation of silica increases the refractive index of the material, producing directly buried waveguides and leaving a flat wafer surface that allows easy integration with further processing steps.

The aim of this thesis is to characterise the physical processes involved in electron-beam irradiation of germanium doped FHD silica and the influence of the different material and irradiation parameters on the change of optical properties. The use of electron-beam irradiation is a convenient way of fabricating different kinds of communication and bio-sensing devices.

To that aim, the germanium-doped flame-hydrolysis silica employed was first characterized. A non-uniformity of the optical properties as a function of depth, was observed. In order to elucidate the origin of the graded-optical properties, compositional, structural and density analyses were carried out on the material. Once the properties of the initial material were known, the effects of electron-beam irradiation were studied. The electron-beam transfers energy to the material non-uniformly, which undergoes a structural rearrangement, which leads to change in the relative density and therefore, variation in the refractive index. The structural, density and refractive index changes were independently characterized and confirmed from theoretical calculations. Thermal annealing experiments were carried out in order to study the stability of the changes induced in the material and further information concerning the physical processes involved was found. Several waveguide devices were fabricated, exhibiting low-losses, thus confirming the suitability of the technique. Finally, the results obtained for electron-beam irradiation were compared with 2 MeV argon ion irradiation, finding that a common structural modification leading to the refractive index change mechanism must be present in both cases.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Supervisor's Name: Cooper, Prof. J.M., Aitchison, Prof. J.S. and De La Rue, Prof. R.
• Date of Award: 2003
• Depositing User: Ms Anikó Szilágyi
• Unique ID: glathesis:2003-5891
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 09 Jan 2015 10:07
• Last Modified: 09 Jan 2015 10:09
• URI: https://theses.gla.ac.uk/id/eprint/5891