Optical nanoantenna helps route information between optical processors

By Warren Miller, contributing writer

Optical computing holds the promise of much faster, smaller, and lower-power processing of complex information. Because light travels much faster than electronic signals and information can be, theoretically at least, coded using small packets of light waves, lower-power and smaller circuits could be used to transmit and process data. Optical computers could therefore be many orders of magnitude more efficient than existing ones. These vastly improved devices still require some significant breakthroughs in implementation, but a recent discovery may have brought them one step closer.

Researchers from Australia and Germany have announced a breakthrough that demonstrates a method for routing information between optical computing elements, a key step in implementing an optical computing system. The project used specialized nanoantennas, located in optical waveguides to control the direction of information flow. This technique allows optical signals that carry information via polarized light to be routed in different directions using silicon waveguides. Similar to the way that wires on an integrated circuit carry electrical signals between computing elements, these waveguides, with the appropriate nanoantennas, could route information carrying optical signals on an optical integrated circuit. Optical waveguides can be made much more compact than on-chip wires, and information can be transferred at the speed of light.

The device couples light of orthogonal polarizations into different directions and modes of the underlying silicon waveguide. Image source: Science Advances.

One of the main reasons I’m intrigued by this breakthrough is that it seems to me to leverage much of what we already know about implementing computers using the traditional electronics approach. Computers are mostly wires connecting logic and storage elements together. At the lowest logical level, data processing and storage is done with logic ‘gates’ that implement simple Boolean logic functions like AND, OR, and NOT. These primitive elements are combined to create more complex and familiar arithmetic, memory, and communications devices. With enough of these elements, you can create a microprocessor.

Using waveguides and nanoantennas to route light-based signals may make it possible to interconnect simple light-based logic elements. Perhaps similar waveguides and nanoantennas can be crafted to create the basic logic gates needed to implement traditional computing circuits. Light signals might be used to change the waveguide properties, which could modify other familiar light-signal-implementing Boolean functions. The result could be an alternative implementation of familiar electronics-based computing systems. This could leverage decades of work on computer architecture and would provide a turbo-boost to computing efficiency.

This breakthrough is not limited to interconnections on-chip, however. Light can travel off-chip too, so interconnections between ‘chips’ could be done using light waves. Perhaps the familiar integrated circuit and printed circuit board concepts will go out the window and chips will be positioned precisely within a nano-manufactured matrix. Connections could be made between holes in the matrix or using special interconnect waveguides, perhaps using a light-based version of the Ethernet protocol. I guess in that case, it could truly be called an ethernet connection.