Radios have five basic components: a power source, a receiver, a transducer, a speaker or headphones, and a tuner. That sounds like radios can never be on an atomic level, but researchers from Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) developed just that.
With building blocks at the size of only two atoms, the world’s smallest radio was made out of an assembly of atomic-scale defects in pink diamonds. It has been successfully played with music at 350 degrees Celsius or about 660 Fahrenheit.
It works through the tiny imperfections in diamonds called nitrogen-vacancy (NV) centers.
As the name suggests, NV centers are systems that are essentially a nitrogen atom with a hole next to it. That is created by replacing one carbon atom in a tiny diamond crystal with a nitrogen atom while removing a neighboring atom.
They have the capacity to emit single photos, detect weak magnetic fields, and covert information into light, making them ideal systems for quantum computing, phontonics, and sensing.
For the smallest radio to work, it is powered through the electrons in diamond NV centers from a green light laser source. Such electrons are sensitive to electromagnetic fields, including the waves used in FM radio.
Once the radio waves enter the NV center, they are converted and emitted as red light. That red light is then transformed into a current by a common photodiode, later produced as sound by a speaker of headphone.
Like other radios, the Harvard tiny radio can also be tuned. There’s an electromagnet that creates a strong magnetic field around the diamond that allows to change the radio station.
The researchers tried to boost the signal of the radio by using billions of NV centers, but the device only works with a single NV center. That means it can only emit one photon at a time rather than a stream of light.
Because it is inside a diamond, the radio is extremely resilient. This property enables this radio to be used in a wide scope of application.
Marko Loncar, leader of the research and Tiantsai Lin Professor of Electrical Engineering at SEAS, elaborates, “Diamonds have these unique properties. This radio would be able to operate in space, in harsh environments and even the human body, as diamonds are biocompatible.”
Linbo Shao, Loncar’s graduate student, co-leads the research. Members of the team include Mian Zhang, Matthew Markham and Andrew M. Edmonds.
Source: Harvard SEAS
