Researchers have demonstrated a laser that can emit microwaves wirelessly, modulate them, and receive external radio frequency signals, enabling it to function as a laser radio transmitter. Previously, the researchers discovered that an infrared frequency comb in a quantum cascade laser could be used to generate terahertz frequencies, the sub-millimeter wavelengths of the electromagnetic spectrum that could move data hundreds of times faster than today’s wireless. It was also found that quantum cascade laser frequency combs could act as integrated transmitters or receivers to efficiently encode information.
Unlike conventional lasers that emit a single frequency of light, laser frequency combs emit multiple frequencies simultaneously — evenly spaced to resemble the teeth of a comb. Inside the laser, the 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 that are within the communications spectrum.
The first thing the device needed to transmit microwave signals was an antenna. To create the antenna, a gap was etched into the top electrode of the device, creating a dipole antenna (like the rabbit ears on the top of an old TV). The frequency comb was modulated to encode information on the microwave radiation created by the beating light of the comb. 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.
It was also demonstrated that the laser radio could receive signals; the behavior of the laser was remote-controlled using microwave signals from another device.