Paving The Way For Light-Based Circuits

We are one step closer to computers that process information through light now that researchers have built optical transistors, multiplexers and signal detectors.

AsianScientist (Dec. 7, 2016) – Researchers in Korea have developed the three key components for building circuits that work with light instead of electrons. Their work, published in Nature Communications, could help speed up how computers process information.

With nanophotonics—the study of light at the nanometer scale—the computers of the future could work almost at the speed of light. However, at nanometer dimensions, the wavelength of light is larger than the diameter of the silicon fiber, and for this reason, some light can be lost.

A solution to control the propagation of light in matter can come from surface plasmons. These are electromagnetic waves that propagate along the surface of some conductive materials like silver, gold, aluminum and copper. Using surface plasmons, optical information can be transmitted nearly at the speed of light, and in extremely small volumes.

Using surface plasmons in silver nanowires and 2D semiconductors like molybdenum disulphide (MoS2), first author Professor Lee Hyun Seok and colleagues from the Institute for Basic Science built three key components for optical communication: optical transistors, optical multiplexers and optical signal detectors. These devices work thanks to a phenomenon called plasmon-exciton-plasmon interconversion.

The researchers constructed the optical transistor by interconnecting the silver nanowire to a flake of MoS2. Light shone on the device is converted to surface plasmons, then to excitons, back to surface plasmons and eventually emitted as light with a shorter wavelength compared to the initial input. For example, if the input light is green, the output light can be red.

Wavelength multiplexing devices were realized in a similar way, but instead of having only a flake of MoS2, the researchers used an array of three different 2D semiconductor materials emitting light at different wavelengths. In this structure, for example, a single input light (violet color) generates three output lights (blue, green and red). The propagating optical signals along the silver nanowire can be also transformed and detected as electrical signals by an optical signal detector.

The article can be found at: Lee et al. (2016) Reconfigurable Exciton-plasmon Interconversion for Nanophotonic Circuits.


Source: Institute for Basic Science.
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