Harvard’s laser radio transmission method lays groundwork for faster Wi-Fi

https://www.digitaltrends.com/computing/harvard-develops-laser-radio-faster-wifi-possible/

A newly discovered method for transmitting radio frequencies wirelessly might bring us a step closer to a future with faster Wi-Fi.According to Engadget, a new method for transmitting radio frequencies wirelessly was developed by researchers at the Harvard University School of Engineering and Applied Sciences. In an update posted on the school’s website, this new method is explained as involving the use of a semiconductor laser to “emit microwaves wirelessly, modulate them, and receive external radio frequency signals.”

While conventional lasers are able to emit single frequencies of light at a time, the laser frequency combs used in the new method are able to emit multiple frequencies at the same time. As noted in Harvard’s post, those frequencies “beat together to generate microwave radiation.” From these laser frequency combs, the researchers were able to generate terahertz frequencies, which are wavelengths capable of moving “data hundreds of times faster than today’s wireless.”

Once the necessary microwaves were generated, the researchers also demonstrated how they transmitted them:

“The first thing the new device needed to transmit microwave signals was an antenna. So, the researchers etched a gap into the top electrode of the device, creating a dipole antenna (like the rabbit ears on the top of an old TV).  Next, they modulated the frequency comb to encode information on the microwave radiation created by the beating light of the comb. Then, using the antenna, the microwaves are radiated out from the device, containing the encoded information.  The radio signal is received by a horn antenna, filtered and sent to a computer. The researchers also demonstrated that the laser radio could receive signals. The team was able to remote control the behavior of the laser using microwave signals from another device.”

The first thing the researchers transmitted was actually a song, Dean Martin’s Volare.

While Harvard’s laser radio transmission method may be a promising first step toward using terahertz frequencies to achieve what the university refers to as “ultra-high-speed Wi-Fi,” it’s still worth mentioning that there is still a ways to go in actually implementing terahertz wireless communication.

The full journal article detailing the researchers work in developing the laser radio transmission method was published in April in the Proceedings of the National Academy of Sciences.

The first laser radio transmitter

This device uses a frequency comb laser to emit and modulate microwaves wirelessly. The laser uses different frequencies of light beating together to generate microwave radiation. The researchers used this phenomenon to send a song wirelessly to a receiver.

Credit: Image courtesy of Marco Piccardo/Harvard SEAS

https://www.sciencedaily.com/releases/2019/04/190425104238.htm

You've never heard Dean Martin like this.

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences transmitted a recording of Martin's classic "Volare" wirelessly via a semiconductor laser -- the first time a laser has been used as a radio frequency transmitter.

In a paper published in the Proceedings of the National Academy of Sciences, the researchers demonstrated a 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 Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, at SEAS and senior author of the study.

This research builds on previous work from the Capasso Lab. In 2017, the researchers discovered that an infrared frequency comb in a quantum cascade laser could be used to generate terahertz frequencies, the submillimeter wavelengths of the electromagnetic spectrum that could move data hundreds of times faster than today's wireless platforms. In 2018, the team found that quantum cascade laser frequency combs could also act as integrated transmitters or receivers to efficiently encode information.

Now, the researchers have figured out a way to extract and transmit wireless signals from laser frequency combs.

Unlike conventional lasers, which emit a single frequency of light, laser frequency combs emit multiple frequencies simultaneously, evenly spaced to resemble the teeth of a comb. In 2018, the researchers discovered that inside the laser, the different frequencies of light beat together to generate microwave radiation. The light inside the cavity of the laser caused electrons to oscillate at microwave frequencies -- which are within the communications spectrum.

"If you want to use this device for Wi-Fi, you need to be able to put useful information in the microwave signals and extract that information from the device," said Marco Piccardo, a postdoctoral fellow at SEAS and first author of the paper.

The first thing the new device needed to transmit microwave signals was an antenna. So, the researchers etched a gap into the top electrode of the device, creating a dipole antenna (like the rabbit ears on the top of an old TV). Next, they modulated the frequency comb to encode information on the microwave radiation created by the beating light of the comb. Then, using the antenna, the microwaves are radiated out from the device, containing the encoded information. The radio signal is received by a horn antenna, filtered and sent to a computer.

The researchers also demonstrated 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 holds great promise for wireless communication," said Piccardo. "While the dream of terahertz wireless communication is still a ways away, this research provides a clear roadmap showing how to get there."

The Harvard Office of Technology Development has protected the intellectual property relating to this project and is exploring commercialization 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.

Terahertz wireless makes big strides in paving the way to technological singularity

Medical AI and doctors at earth stations could remotely conduct a zero-gravity operation aboard a space plane connected via terahertz wireless links.(CREDIT ©HIROSHIMA UNIVERSITY, NICT, PANASONIC, AND 123RF.COM)

https://www.eurekalert.org/pub_releases/2019-02/hu-twm021419.php

Hiroshima, Japan, February 19, 2019--Hiroshima University, National Institute of Information and Communications Technology, and Panasonic Corporation announced the successful development of a terahertz (THz) transceiver that can transmit or receive digital data at 80 gigabits per second (Gbit/s). The transceiver was implemented using silicon CMOS integrated circuit technology, which would have a great advantage for volume production. Details of the technology will be presented at the International Solid-State Circuits Conference (ISSCC) 2019 to be held from February 17 to February 21 in San Francisco, California [1].

The THz band is a new and vast frequency resource expected to be used for future ultrahigh-speed wireless communications. IEEE Standard 802.15.3d, published in October 2017, defines the use of the lower THz frequency range between 252 gigahertz (GHz) and 325 GHz (the "300-GHz band") as high-speed wireless communication channels. The research group has developed a single-chip transceiver that achieves a communication speed of 80 Gbit/s using the channel 66 defined by the Standard. The research group developed a 300-GHz-band transmitter chip capable of 105 Gbit/s [2] and a receiver chip capable of 32 Gbit/s [3] in the past few years. The group has now integrated a transmitter and a receiver into a single transceiver chip. 

"We presented a CMOS transmitter that could do 105 Gbit/s in 2017, but the performance of receivers we developed, or anybody else did for that matter, were way behind [3] for a reason. We can use a technique called 'power combining' in transmitters for performance boosting, but the same technique cannot be applied to receivers. An ultrafast transmitter is useless unless an equally fast receiver is available. We have finally managed to bring the CMOS receiver performance close to 100 Gbit/s," said Prof. Minoru Fujishima, Graduate School of Advanced Sciences of Matter, Hiroshima University.

"People talk a lot about technological singularity these days. The main point of interest seems to be whether artificial superintelligence will appear. But a more meaningful question to ask myself as an engineer is how we can keep the ever-accelerating technological advancement going. That's a prerequisite. Advances in not only computational power but also in communication speed and capacity within and between computers are vitally important. You wouldn't want to have a zero-grav operation on board a space plane without real-time connection with earth stations staffed by medical super-AI and doctors. After all, singularity is a self-fulfilling prophecy. It's not something some genius out there will make happen all of a sudden. It will be a distant outcome of what we develop today and tomorrow," said Prof. Fujishima.

"Of course, there still is a long way to go, but I hope we are steadily paving the way to such a day. And don't you worry you might use up your ten-gigabyte monthly quota within hours, because your monthly quota then will be in terabytes," he added.