Scientists build world’s smallest radio receiver

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The building blocks of the world’s smallest radio receiver consist of tiny defects in pink diamonds — defects the size of two atoms.

The record-setting receiver was built by researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences.

The man-made defects are called nitrogen-vacancy centers. Scientists replace a single carbon atom in a diamond with a nitrogen atom. A neighboring atom is removed entirely. The result is a nitrogen atom saddled next to a hole.

The most useful property of an NV center is photoluminescence. The centers convert information into light and can be manipulated by the application of a magnetic field, electric field, microwave radiation or light. The centers’ photoluminescence can be utilized for quantum computing, bioimaging and other optical technologies.

Scientists at Harvard used the defects to build a radio receiver by exciting the centers with a green laser. The electrons expelled by the process are sensitive to electromagnetic fields, like radio waves. The radio waves impact the defect’s electrons, causing the center to emit photons of red light. The red light is converted into electric current by a photodiode and into sound by a speaker.

An electromagnetic field surrounding the diamond can be manipulated to change the radio station by limiting the frequencies received by the nitrogen-vacancy centers.

The diamond’s durability makes the radio resilient. Scientists successfully played music at temperatures upwards of 660 degrees Fahrenheit. Though multiple defects can be combined the produce a louder signal, the radio can also function using single laser photons fired into a solitary nitrogen-vacancy center.

“Diamonds have these unique properties,” Marko Loncar, a professor a electrical engineering at Harvard, said in a news release. “This radio would be able to operate in space, in harsh environments and even the human body, as diamonds are biocompatible.”