Photons, or units of light, are faster than electrons and could, therefore, process information faster from smaller chip structures. A switch was designed that bypasses a tendency for the unwanted absorption of light when using surface plasmons, or light coupled to oscillations of free electron clouds, to help confine light to a nanoscale. Even though plasmonics downsizes light, photons also get lost, or absorbed, rather than transferred to other parts of the computer chip when they interact with plasmons.

This artistic rendering magnifies a switch developed within a computer chip to control for loss of photons when light is reduced to a nanoscale. (Virginia Commonwealth University image/Nathaniel Kinsey)

Researchers addressed this problem through the development of a switch, called a ring modulator, that uses resonance to control whether light couples with plasmons. When on, or out of resonance, light travels through silicon waveguides to other parts of the chip. When off, or in resonance, light couples with plasmons and is absorbed.

With a purely plasmonic device, light can be lossy; however, in this case, it reduces a signal when necessary. The loss creates a contrast between on and off states, thus better enabling control over the direction of light where appropriate for processing bits of information. A plas-mon-assisted ring modulator also results in a smaller “footprint” because plasmons enable confinement of light down to nanoscale chip structures.

The researchers plan to make this modulator fully compatible with complementary metal-oxide-semiconductor transistors, paving the way to truly hybrid photonic and electronic nanocircuitry for computer chips.

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