Featuring building blocks the size of two atoms, the radio can withstand harsh environments and is biocompatible. “Diamonds have unique properties,” said Professor Marko Loncar. “This radio would be able to operate in space, in harsh environments and even the human body, as diamonds are biocompatible.”
The radio uses imperfections in diamonds called nitrogen vacancy (NV) centres. To make them, researchers replace one carbon atom in a diamond crystal with a nitrogen atom, then remove a neighbouring atom. This creates a system featuring a nitrogen atom with a hole next to it. NV centres, which can emit single photons or detect very weak magnetic fields, also have photoluminescent properties, meaning they have potential application in quantum computing, phontonics and sensing.
In the Harvard device, electrons in diamond NV centres are pumped by green light emitted from a laser. When the NV centre receives radio waves, it converts them and emits the audio signal as red light. A photodiode converts light into a current, which is converted to sound through a simple speaker.
The tuning frequency of the NV centre can be changed using an electromagnet.
Prof Loncar and graduate student Linbo Shao used billions of NV centres in order to boost the signal, but say the radio can work with a single NV centre, emitting one photon at a time, rather than a stream of light.
And, because of the inherent strength of diamond, the team played music successfully at 350°C.
