Parallel three-dimensional free-space optical interconnection for an optoelectronic processor

A hybrid scalable optoelectronic crossbar switching system that uses global parallel free-space optical interconnects and three-dimensional (3D) VLSI chip stacks is presented. The system includes three 3D chip stacks with each consisting of 16 VLSI chips. A single 16 × 16 VCSEL/MSM detector array is flip-chip bonded on top of the chip stack. Each chip supports 16 optical I/Os at 1 Gb/s. For the free-space optical interconnection between the chip stacks, a novel folded hybrid micro/macro optical system with a concave reflection mirror has been designed. The optics module can provide a high resolution, large field of view, high link efficiency, and low optical crosstalk. It is also symmetric and modular. Off-the-shelf macro-optical components are used. The concave reflection mirror can significantly improve the image quality and tolerate a large misalignment of the optical components. Scaling of the macrolens can be used to adjust the interconnection length between the chip stacks. The optical system is analyzed based on ray-tracing and scalar diffraction theory. The impact of Ghost talk on high-speed optical interconnection is studied. For system packaging, only passive alignment is required. Optics and electronics are separated until final assembly step, and the optomechanic module can be removed and replaced. By using 3D chip stacks, commercially available optical components and simple passive packaging techniques, it is possible to achieve a high-performance optoelectronic switching system.