Scientists have created the world’s smallest radio receiver out of minute imperfections only two atoms thick within pink diamonds.
The tiny receiver is able to withstand extreme temperatures and is biocompatible, thus making it potentially applicable in the fields of space travel and medicine, say the researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) at Harvard University.
“Many modern applications require small and robust receivers that could operate in high temperature (>100 °C), high pressure, and/or a chemically harsh environment,” say the study’s authors, whose work is published in the journal Physical Review Applied.
Diamonds are truly remarkable things. Rarely flawless, they often come with a range of imperfections within their crystal latticework, often making for interesting properties.
One type of flaw created in the lab or in nature is nitrogen vacancy, which occurs when individual carbon atoms in the diamond are displaced through irradiation to produce a unique pattern, with one nitrogen atom sitting next to essentially a hole in the carbon latticework (hence the term nitrogen vacancy or NV). The special property of this imperfection is that it makes the compound photo-luminescent, meaning that the latticework can emit light in the form of photons when an electric, magnetic or even light wave charge is applied to it.
In this case, researchers flushed the pink diamond with green light, causing the electrons in its NV centres to be responsive to electromagnetic fields such as a radio signal and to emit photons of red light in response.
“Our device takes advantage of the fact that the photoluminescence of an NV center depends on its electron spin state, which is sensitive to microwave radiation,” say the study’s authors, who were able to manipulate the magnetic field around the diamond in order to adjust the frequency reception.
The principle works on the atomic level, as all it takes is one NV centre emitting one photon to create the radio signal, but in fact, billions of NV centres in the one diamond fragment were used in tandem to produce the result –here, playing Christmas music.
And because this radio is made from a diamond, it can withstand high temperatures while still functioning. In fact, the researchers found that their little boombox still played at 350 degrees Celsius, making it potentially useful on space missions to extreme environments, such as sending a probe to the hot surface of Venus.
“Diamonds have these unique properties,” says Marko Loncar, the Tiantsai Lin Professor of Electrical Engineering at SEAS and lead author of the study. “This radio would be able to operate in space, in harsh environments and even in the human body, as diamonds are biocompatible.”
Radio waves were first manipulated to deliver communication over long distances by Guglielmo Marconi in the 1890s, with the first transatlantic telegraph signal being delivered in 1901, linking Cornwall, England, to Signal Hill in St. John’s Newfoundland.
Although Marconi’s successes with radio telegraphy are well known, the transmission of audio and voice over radio waves via a continuous wave transmitter is a lesser known milestone, one accomplished by Canadian inventor, Reginald A. Fessenden, who delivered the first public radio broadcast on Christmas Eve, 1906. The program included Fessenden himself playing the Christmas carol O Holy Night on the violin.
Below: A diamond radio receiver