Laser frequency combs may be the future of Wi-Fi

Wi-Fi and cellular data traffic are increasing exponentially but, unless the capacity of wireless links can be increased, all that traffic is bound to lead to unacceptable bottlenecks.

Upcoming 5G networks are a temporary fix but not a long-term solution. For that, researchers have focused on terahertz frequencies, the submillimeter wavelengths of the electromagnetic spectrum. Data traveling at terahertz frequencies could move hundreds of times faster than today's wireless.

In 2017, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) discovered that an infrared frequency comb in a quantum cascade laser could offer a new way to generate terahertz frequencies. Now, those researchers have uncovered a new phenomenon of quantum cascade laser frequency combs, which would allow these devices to act as integrated transmitters or receivers that can efficiently encode information.

The research is published in Optica.

"This work represents a complete paradigm shift for the way a laser can be operated," said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering and senior author of the paper. "This new phenomenon transforms a laser—a device operating at optical frequencies—into an advanced modulator at microwave frequencies, which has a technological significanceforefficient use of bandwidth in communication systems."