Laser frequency 'combs' could improve wireless capacity, claim Harvard scientists

The scientists claim that laser 'comb' technology could radically improve wireless network performance

Harvard scientists claim to have found a way to use laser frequency 'combs' to increase the speed and capacity of wireless communications.

In 2017, the Harvard University research team placed an infrared frequency comb in a quantum cascade laser to generate an influx of terahertz frequencies.

Now they have discovered a new phenomenon of laser frequency combs that could see them "act as integrated transmitters or receivers that can efficiently encode information".

Wireless traffic data is expected to continue growing for the foreseeable future, leading to fears of bottlenecks at some point.

Although 5G technology is expected to improve latency, the researchers claim that it will only be a temporary fix. This led them to look for a long-term solution.

They believe that terahertz frequencies, which are submillimeter wavelengths of the electromagnetic spectrum, could be the answer. The latter has the potential to move data hundreds of times faster than current systems.

Federico Capasso, a research fellow at the university, said this study "represents a complete paradigm shift for the way a laser can be operated".

He explained: "This new phenomenon transforms a laser - a device operating at optical frequencies - into an advanced modulator at microwave frequencies, which has a technological significance for the efficient use of bandwidth in communication systems."

With frequency tools, technologists are able to measure and detect different light frequencies with high precision.

This technology tends to outflank conventional lasers because it can handle multiple frequencies simultaneously.

Currently, it is used for a range of purposes, such as measuring fingerprints and locating distant exoplanets. But the researchers believe that it is capable of much more.

"We were interested in what was going on inside the laser, in the laser's electron skeleton," said Marco Piccardo, who also worked on the project. "We showed, for the first time, that a laser at optical wavelengths can operate as a microwave device."

The most promising aspect of the lasers is that they can combine different light frequencies to create microwave radiation.

Capasso and Piccardo found that this process causes electrons to oscillate, which could be harnessed to encode information in wireless technology.

Piccardo claimed that this functionality has never been demonstrated in a laser before.

"We have shown that the laser can act as a so-called quadrature modulator, allowing two different pieces of information to be sent simultaneously through a single frequency channel and successively be retrieved at the other end of a communication link," he said.

Capasso added: "Currently, terahertz sources have serious limitations due to limited bandwidth."This discovery opens up an entirely new aspect of frequency combs and could lead, in the near future, to a terahertz source for wireless communications."