Ph.D. Proposal Presentation by
Shashikant G. Hegde
Friday, May 20, 2005
(Dr. Suresh Sitaraman, Chair)
"Effect of Thermal and Mechanical Factors on Reliability and Optical Loss in High-Speed Optoelectronic Packaging"
Currently high-speed electrical interconnects in electronic systems are facing bandwidth limitations due to signal attenuation at high frequencies and small aspect ratios. Through the integration of optoelectronic packages into electronic systems, optics has the potential to revolutionize package-level interconnects in electronic systems, the same way as it did for long-range communication. The components of an optoelectronic package include optically active devices such as laser and detector arrays, and passives such as waveguide interconnects and mirrors. The loss in optical power and signal quality in these components is significantly affected by temperature and mechanical stresses. For high-speed optoelectronic packaging to be successfully integrated within electronic systems, in a way that is manufacturable and cost-effective, an investigation into the effects of thermal and mechanical factors on optical loss and reliability of its components is critical.
In this work, polymer waveguides are fabricated and the effects of temperature and stress on them are studied using experiments and numerical models. Thermo-mechanical stresses in a polymer waveguide can cause an anisotropic change in refractive index called birefringence. A novel method has been developed to extract the stress-optical coefficients of a polymer, and use it to determine the stress-induced birefringence in a waveguide. Long-term reliability of polymer waveguides has also been evaluated. The change in optical loss of waveguide during thermal aging and thermal cycling tests has been determined, and fitted with analytical models to yield interesting and significant trends. T o study the thermal characteristics of a laser package a power dissipation experiment is performed. Numerical models are then developed to study the thermal and mechanical characteristics of optoelectronic packages such as: misalignment due to thermal expansions and contractions, temperature distribution, tensile and interfacial stresses.