Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences published a paper in the Proceedings of the National Academy of Sciences outlining their demonstration of their laser that can emit microwaves wirelessly, modulate them, and receive external radio frequency signals.
“The research opens the door to new types of hybrid electronic-photonic devices and is the first step toward ultra-high-speed Wi-Fi,” said Federico Capasso, the senior author of the study and Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS.
The laser was made possible thanks to research done in 2017 at the Capasso Lab, in which researchers discovered that they could generate terahertz frequencies— the submillimeter wavelengths of the electromagnetic spectrum that move data much faster than today’s wireless—using an infrared frequency comb in a quantum cascade laser. In 2018, they found quantum cascade laser frequency combs were able to act as integrated transmitters or receivers to efficiently encode information and that inside the laser, the different frequencies of light beat together to generate microwave frequencies — which are within the communications spectrum.
With this year’s discovery, the researchers have been able to extract and transmit wireless signals from laser frequency combs so that they can put in and take out useful, communications-based information from the microwave radiation.
From all this new information, the team created a device that uses a dipole antenna to transmit microwave signals and modulated the frequency comb to encode information on the microwave radiation created by the beating light of the comb. Microwaves containing the encoded information are radiated out from the device, thanks to the antenna, then a horn antenna receives a radio signal, which is filtered and sent to a computer.
“This all-in-one, integrated device, holds great promise for wireless communication,” said Marco Piccardo, a postdoctoral fellow at SEAS and first author of the paper. “While the dream of terahertz wireless communication is still a ways away, this research provides a clear roadmap showing how to get there.”
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