Chipmakers are constantly seeking innovative ways to reduce power consumption, heat production, and component volumes of compact electronics. Technology developments have increased the end-user demands for faster and more efficient systems, requiring either improved clock-speed or multicore processors and subsequent complex inter-core communication. Both alternatives suffer significant drawbacks, as increased clock speed results in higher power consumption and internal heat production, while efficient inter-core communication using complex wire bus systems takes up space, consumes energy, and produces excess heat. Optical fibers are currently the best solution in the market for internal heat reduction. However, they are still limited by complex wiring networks and one-dimensional optical data transmission. There is a need for a more efficient, less complex solution that will enable better multicore processor connectivity.

This invention involves a compact optical bus that is comprised of a planar waveguide on silicon chips, where light is confined in a layer by total internal reflection. The layer is made of silicon sandwiched between silica layers (glass), while the inner silicon layer has a high refractive index compared to the upper and lower silica layers. The height of the highly refractive layer is carefully designed to provide a specific refractive index profile dictated by the layer thickness. A light management system selectively activates specific illumination ports embedded within the waveguide; the emanating light is then focused onto reflectors (Bragg mirrors), leading to light ray emission at specific partner points. The light can be simultaneously focused onto a plurality of photodetectors within the waveguide, each communicating with a separate processor core. The optical bus can be designed in several geometries, reaching very high core densities, and can be adjusted to match computer processor or core layout requirements to overcome the need for physical wiring (see Figure below). 

A) Schematic top view of a propagation layer of the optical bus depicting light propagation from a divergence point to convergence at multiple focal points for a circular (left), square (middle), or spiral (right) embodiment of the optical bus. B) A top view (left) and a side view (right) of a prototype manufactured by an e-beam lithography taken with electron microscope. C) Schematic cross-sectional view of an optical bus. Upper (1) and lower (3) non-propagation layers; light propagation layer (2), and a Bragg mirror (4). The effective refractive index defined by the thickness profile of the propagating silicon layer causes light propagation to follow specific propagation paths with unique and exclusive sets of focal points.