Alex Fritze:
"Integration of Optoelectronic Devices, 
Electronic Circuitry and Optical Waveguides"

PhD Thesis, Heriot-Watt University 2002

Abstract:

This thesis explores the technological issues of optically
interconnecting electronics by integrating optoelectronic devices with
digital electronic circuitry and optical polymer waveguides on a
common substrate, utilising direct-laser writing and polymer flip-chip
bonding.  The work is presented in the context of an optoelectronic
crosspoint switch demonstrator, which will combine high-speed logic
circuitry with vertical-cavity surface-emitting lasers (VCSELs),
photodetectors and multimode waveguides.

A study of "surface-normal" optoelectronic devices is presented. This
work encompasses characterisation and modelling of multiple-quantum
well modulators (MQWMs) by curve-fitting experimental data to a
semi-empirical device model. For VCSELs, an analysis of the dynamic
lasing behaviour under various pre-bias conditions is presented.

Waveguide fabrication based on photopolymerisation of mulifunctional
acrylate polymers utilising direct laser-writing is described. An
experimental setup based on a 325nm HeCd laser and a mechanical
translation stage is presented, and the writing process is modelled.
Experimental results for multimode waveguides written in a
PMMA/diacrylate-based polymer are presented. Tapered direct writing
onto fibre-ends and direct writing of 45°-turning mirrors are explored
as methods for interfacing waveguides to external components.

A novel low-temperature compliant polymer flip-chip bonding process is
presented.  In this process, both fabrication of bumps and
metallisation-masking are accomplished utilising the same direct
laser-writing setup used for waveguide writing. The bump-formation
process is characterised and experimental results of bumps written in
a commercial photopolymer (Norland NOA-61) are presented. A process
for integrating flip-chip bumping/metallisation and polymer waveguide
fabrication is discussed.