A team of researchers has built an exciting new device to dramatically amplify microwave signals. It seems like a science fiction MacGuffin: it uses a purple diamond in a quartz tube exposed to an intense magnetic field. The system creates a maser, the microwave equivalent of a laser. It is used to amplify weak microwave and radio signals.

Amplifiers are very useful and not just for music concerts. With the right tech, any signal can be made clearer. An example is the signals from the Voyager probes, which continue to talk to Earth four decades into their mission, now well into interstellar space. Their amplifiers are key to getting the signal out, but require very cold temperatures to operate. The new one, however, works at room temperature.

"The microwaves enter the device and then the spins inside the diamond create copies of them, which in effect amplifies the microwave signals. Ideally, the microwave signals then come out much larger and with very little noise on top," senior author Associate Professor Jarryd Pla, from the University of New South Wales, said in a statement.

The researchers have shown that the setup can amply the signal by a factor of up to 1,000. It could be used to receive data from spacecraft but also from microwave-emitting sources such as pulsars, black holes, and whole galaxies.

"Currently, electronic amplifiers are being used to detect signals from very distant spacecraft like Voyager 1 which is now more than 15 billion miles away from Earth, but still sending out data,” Pla continued.

"Those amplifiers are cryogenically cooled to reduce what is known as thermal noise, which is random electrical noise generated by the motion of electrons in the amplifier's components. Otherwise, that noise would just overwhelm the signals being received." 

"Our room temperature solid-state maser amplifier avoids all the complication and cost of having to cool everything down to extremely low temperatures and is also much more compact."

The diamond’s color is not for aesthetic reasons. It is caused by specific defects called nitrogen vacancy (NV) centers, where a nitrogen atom is put in place of a carbon atom next to an empty spot. These spin systems, as they are called, are key to the amplification. Adding a lot of these imperfections (up to a point) is key to the tech, hence why the diamond is purple.  

"In effect, we need to make the diamonds more purple," lead author Tom Day explained. "The purple color is actually caused by red light emitted by the NV centers. Making darker samples means more NV centers, which ultimately produces higher levels of gain and lower levels of noise and makes the amplified signals clearer.”

The team has stated that there are challenges to making the device even better, but it could be commercially available in just a few years.

The study is published in the journal Physical Review X.