Integration of Optoelectronic Devices, Electronic Circuitry and Optical Waveguides

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 325 nm 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.