The Smallest Radio Receiver Ever Is Made from Imperfections in Diamonds

Harvard researchers made the world’s smallest radio receiver by using atomic imperfections in a pink diamond.
December 17, 2016, 8:00pm

Researchers at Harvard's School of Engineering and Applied Sciences (SEAS) have made the world's smallest radio receiver by levering atomic level imperfections in pink diamonds.

According to the researchers, this radio receiver is incredibly durable and would be ideal for future deployment in harsh environments ranging from the human body to atmosphere of Venus. In fact, they were able to play music on the radio at temperatures of up to 660 Fahrenheit, just 200 degrees shy of the average Venusian temperature, but nearly 500 degrees higher than the average consumer radio.

As detailed in a paper published in Physical Review Applied this week, the SEAS diamond radio works by taking advantage of imperfections in the diamonds called nitrogen vacancy centers.

The researchers were able to create these imperfections in the diamond by replacing a carbon atom with a nitrogen atom and then removing the carbon atom directly next to it. In essence, this creates a hole in the diamond's atomic lattice of carbon atoms that can be used to channel individual photons or detect weak magnetic fields.

Typical radios are composed of five elements, namely: a power source, a receiver, a transducer (which converts electromagnetic waves into an electric current), a tuner and a speaker. The Harvard device also has all of these elements, albeit highly exotic versions of them.

The power source in the Harvard radio is green light emitted from a laser that are beamed at the electrons in the nitrogen vacancy centers. These electrons are sensitive to electromagnetic fields, so once they are excited by the laser they can pick up radio waves. When the nitrogen vacancy center detects radio waves, it converts them into red light that is channeled through a photodiode (the transducer in this case) that converts the light into an electrical current. This electrical current can then be turned into sound by using a speaker or headphones.

But what about the tuner, you might ask. How does one change the radio station when your radio receiver is only two atoms wide? To do this, the SEAS researchers created a magnetic field around the diamond which they could manipulate to change the receiving frequency of the nitrogen vacancies. The signal can be boosted by using more nitrogen vacancy centers (the researchers used billions of these imperfections), but it also works with only a single imperfection. In this case, however, that nitrogen vacancy would only be emitting a single photon at a time, instead of a stream of red light.

In the future, the team hopes to explore how other atomic defects—such as silicon vacancy centers in diamonds—can be used to manipulate radio waves.