Cellular data and Wi-Fi traffic are growing at an exponential pace, so is the need to increase the capacity of wireless links. Unless we find a way to accomplish it, the rising traffic is bound to lead to unmanagable bottlenecks.
Taking this thought forward, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a method to transmit radio frequency wirelessly through a semiconductor laser.
This breakthrough establishes the fact that lasers can be used to emit microwaves, modulate them and receive external radio frequency signals — thus opening up a whole new possibility of achieving “ultra-high-speed WiFi.”
The research, published in Proceedings of the National Academy of Sciences, explains how an infrared frequency comb in a quantum cascade laser could be used to generate terahertz frequencies.
The team has also discovered a new phenomenon of quantum cascade laser frequency combs, which allows devices to act as integrated transmitters or receivers where information can be efficiently encoded in signals.
For the uninitiated, frequency combs are high-precision tools used for measuring and detecting different frequencies like colors of light. Unlike conventional lasers, which emit a single frequency, frequency combs can emit multiple frequencies simultaneously.
These signals resemble the teeth of a comb, and they can be used for everything — from fingerprinting specific molecules to detecting distant exoplanets.
But in this case, researchers were interested in knowing what goes inside a laser beam. For the first time, it has been established that a “laser at optical wavelengths operates as a microwave device.”
It was found that “different frequencies of light beat together to generate microwave radiation.” The light inside the cavity of the laser causes electrons to oscillate at microwave frequencies (within the communications spectrum).
These oscillations can be externally modulated to encode information using a carrier signal. For the first time, such functionality has been demonstrated in a laser.
The first thing transmitted through the laser radio waves was the song “Volare” by Dean Martin, even though it’s a 15-second track.
In any case, this discovery could become the key to achieving Wi-Fi speeds hundreds of times faster than today’s wireless internet services.