Alignment and packaging techniques for two-dimensional free-space optical interconnects

Two-dimensional free-space optical interconnects (2D-FSOIs) promise to deliver tremendous gains in bandwidth and architectural freedom for applications such as telecommunication switches and massively parallel computing systems. One major obstacle preventing the commercial deployment of 2D-FSOI systems is the problem of optical alignment, which is further exacerbated by the requirements that these systems be field-serviceable and able to sustain the harsh conditions of industrial environments.This thesis proposes a broad range of solutions to alleviate this alignment problem. One important aspect of this work concerns the development of a generic packaging strategy, which consists of partitioning an optical system into separate modules in such a way that the loose tolerances are between the modules while the tight tolerances are between the components inside the modules. To accomplish this, novel alignment techniques are designed and demonstrated, including the use of integrated diffractive features, CMOS position detectors, ultrathick photoresist micro-structures, and semi-kinematic fixtures using dowel pins. In all cases, emphasis is placed on approaches that are amenable to low-cost manufacturing and high-volume production.These techniques were developed in the context of a photonic backplane prototype experiment that demonstrated 1024 free-space interconnections between four optoelectronic-VLSI (OE-VLSI) chips. The design and implementation of a module integrating an OE-VLSI chip, a mini-lens array, a thermoelectric cooler and a heatsink is presented. Optomechanical, electrical and thermal characterization results are reported.The other aspect of this work aims at identifying the types of optical designs that provide more generous misalignment tolerances. This is done by investigating various optical configurations for the design of the chip module. The central objective is to understand the underlying reasons that make one configuration more misalignment-tolerant than another. A significant outcome of this work is to show that the inherent misalignment tolerances of 2D-FSOI systems translates into an aspect-ratio limitation similar to the one found in electrical interconnects