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Boffins have made optical transistors that can reach 4 TERAHERTZ

Practical application could take years to reach, though

Aluminum-doped zinc oxide is the key to building faster, optical chips, according to researchers at Purdue University, Indiana.

They've modelled an all-optical, CMOS-compatible transistor capable of 4THz speeds, potentially more than 1,000 times faster than silicon transistors.

The all-optical bit means that the data stream and the control of the switching is optical; previous optical transistors have used electrical control and optics for data. This has inhibited the switching speed. The use of aluminum-doped zinc oxide (AZO) opens up the opportunity for both.

It is very much aimed at optical switching rather than building processors, and according to the researchers, the optical transistors have a tunable dielectric permittivity compatible with all telecoms infrared (IR) standards.

“We are pretty far away from building anything resembling an processor. In fact our transistor is only simulation at the current time," said doctoral candidate Nate Kinsey, in conversation with El Reg.

"However, we have taken care to use realistic parameters so that the performance should be very similar to our simulations,” he added.

He explained that one issue is that the transistor is controlled with UV light, and this "is really not that practical for a highly integrated device. We envisioned our switch being more of use for ultra-small signal encoding, say in like a data centre".

Even the stages of developing something simpler, such as an adder, multiplier, or a gate poses problems, Kinsey explained, as the "things you're discussing you need light of the same wavelength in the signal and the control, so that the output of one transistor can control another".

"This is how you would build logical circuits. With our current system that uses a carrier of 1300nm and a control of 350nm, this would be extremely difficult to achieve," he added.

"However, in principle our device could be thought of as a stepping stone to such a system, as controlling light with light is somewhat difficult as photons do not interact with other photons like electrons do," Kinsey said.

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