You've never listened to Dean Martin like that.
Researchers from the Harvard School of Engineering and Applied Sciences John A. Paulson wirelessly transmitted a recording of Martin's clbadic "Volare" through a semiconductor laser, the first time a laser was used as a radiofrequency transmitter.
In an article published in the Procedures of the National Academy of Sciences, the researchers demonstrated a laser that can emit microwaves wirelessly, modulate them and receive external radiofrequency signals.
"Research opens the door to new types of electronic-photonic hybrid devices and is the first step towards an ultra-high-speed Wi-Fi connection," said Federico Capbado, professor Robert L. Wallace of Applied Physics and senior researcher Vinton Hayes at Electrical Engineering, in SEAS and main author of the study.
This research is based on previous works of the Capbado laboratory. In 2017, the researchers discovered that an infrared frequency comb could be used in a quantum cascade laser to generate terahertz frequencies, the submillimeter wavelengths of the electromagnetic spectrum that could move data hundreds of times faster than current wireless platforms. In 2018, the team discovered that quantum cascade laser frequency combs could also act as integrated transmitters or receivers to encode information efficiently.
Now, researchers have discovered a way to extract and transmit wireless signals from the laser frequency combs.
Unlike conventional lasers, which emit a single frequency of light, the laser frequency combs emit multiple frequencies simultaneously, spaced evenly to resemble the teeth of a comb. In 2018, researchers discovered that within the laser, different frequencies of light pulsed together to generate microwave radiation. The light inside the laser cavity caused the electrons to oscillate at microwave frequencies, which are within the communication spectrum.
"If you want to use this device for Wi-Fi, you should be able to put useful information into microwave signals and extract that information from the device," said Marco Piccardo, SEAS postdoctoral fellow and first author of the article. .
The first thing the new device needed to transmit microwave signals was an antenna. Therefore, the researchers recorded a hole in the upper electrode of the device, creating a dipole antenna (like the rabbit ears on top of an old TV). Next, they modulated the frequency comb to encode the information about the microwave radiation created by the comb's beating light. Then, using the antenna, the microwaves are irradiated from the device and contain the encoded information. The radio signal is received by a horn antenna, filtered and sent to a computer.
The researchers also showed that the laser radio could receive signals. The team was able to remotely control the behavior of the laser using microwave signals from another device.
"This all-in-one integrated device is a great promise for wireless communication," said Piccardo. "While the dream of terahertz wireless communication is still far away, this research provides a clear roadmap that shows how to get there."
The Harvard Technology Development Office has protected the intellectual property related to this project and is exploring marketing opportunities.
This research was co-authored by Michele Tamagnone, Benedikt Schwarz, Paul Chevalier, Noah A. Rubin, Yongrui Wang, Christine A. Wang, Michael K. Connors, Daniel McNulty and Alexey Belyanin. It was supported in part by the National Science Foundation.