Silicon multiplexer chips will drive the development of 6G next-generation communications

A new design of ultra-small silicon chip, called a multiplexer, will efficiently manage terahertz waves, which is key to next-generation communications such as 6G. Researchers from Osaka University in Japan and the University of Adelaide in Australia worked together to produce a new multiplexer made of pure silicon for terahertz range communications in the 300GHz band.

To harness the vast spectral bandwidth of terahertz waves, multiplexers, which are used to split and connect signals, are essential to breaking the information into manageable chunks that can be processed more easily and therefore transferred more quickly from one device to another.

Until now, no compact and practical multiplexer has been developed for the terahertz range, the researchers say. The new terahertz multiplexer is economical to manufacture and will be extremely useful for ultra-wideband wireless communications. The shape of the developed chip is key to combining and splitting channels, which allows more data to be processed more quickly. Its simplicity is its charm.

People around the world are increasingly using mobile devices to access the internet, and the number of connected devices is increasing exponentially. Soon, machines will communicate with each other in the Internet of Things, which will require ever more powerful wireless networks capable of quickly transmitting large amounts of data. Terahertz waves are part of the electromagnetic spectrum with a raw spectral bandwidth far wider than conventional microwave-based wireless communications. The team has developed ultra-compact and efficient terahertz multiplexers thanks to a novel optical tunneling process.

"A typical four-channel optical multiplexer might span more than 2,000 wavelengths. In the 300 GHz band, that would be about two meters in length. Our device has just 25 wavelengths, which is a massive 6,000-fold reduction in size. The new multiplexer covers more than 30 times the total spectrum allocated in Japan for 4G/LTE (currently the fastest mobile technology) and 5G (the next generation). Because bandwidth is related to data rate, ultra-high-speed digital transmissions can be achieved using the new multiplexer.

The current four-channel multiplexer has the potential to support a total data rate of 48Gbit/s per second, equivalent to real-time streaming of uncompressed 8K ultra-high-definition video. The research, published in the journal Optica, was funded by the Japan Science and Technology Agency (JST) CREST Grant, a KAKENHI grant, and an Australian Research Council (ARC) grant. The current work builds on the team's 2020 work, when they created substrate-free, metal-free silicon microphotonics for the efficient integration of terahertz devices. This innovation opens a path to convert existing nanophotonic multiplexers to the terahertz realm.