‘Earthquake on a chip’ uses ‘phonon’ lasers to make mobile devices more efficient
Engineers created a device that produces tiny earthquake-like vibrations on the surface of a chip. They say it could one day be harnessed for signal processing in everyday electronics, potentially paving the way for smaller, faster and more efficient wireless devices.
In a new study published January 14 in the journal Naturethe scientists described their device as a surface acoustic wave (SAW) phonon laser which generates very small, rapid vibrations.
In nature, SAWs are produced on a large scale when tectonic plates slide against each other and cause earthquakes.
SAWs are also used as filters in smartphones to help clean up wireless signals. A telephone’s radio receives radio waves coming from a cell phone tower, then converts them into tiny mechanical vibrations, making it easier for the chips to eliminate unwanted noise.
Multiple chips convert radio waves to SAW and vice versa every time you send a text message, make a call, or access the Internet.
SAWS in modern technology
Although conceptually similar to surface seismic waves emitted by earthquakes, SAWs are far too small to be measured on a scale such as the moment magnitude scale, used to estimate the energy released by the movement of the Earth’s crust.
SAW devices are essential to many of the world’s most important technologies, lead study author Matt Eichenfieldprofessor of quantum engineering at the University of Colorado at Boulder, said in the release. This includes cell phones, key fobs, garage door openers, most GPS receivers, and radar systems.
The scientists said a single, all-solid-state chip that generates coherent SAWs at very high frequencies, without the need for an external radio frequency source, has never been achieved before.
Traditional SAW components typically require two separate chips and a power source. The team’s design aimed to deliver similar functionality using a single chip, potentially allowing much higher frequencies to be powered by a typical smartphone battery.
The researchers built the device by stacking ultrathin layers of different chip materials into a tiny “bar” about 0.02 inches (0.5 millimeters) long.
This included a silicon base; a thin layer of lithium niobate, a type of piezoelectric crystal which converts electrical signals into mechanical vibrations; and a final layer of indium gallium arsenide, a semiconductor material capable of accelerating electrons to extremely high speeds when exposed to an electric field.
The system works by repeatedly amplifying vibrations as they bounce within the structure, similar to how light intensifies in an environment. diode laser between two mirrors. The surface vibrations of the lithium niobate interact with the electrons of the indium gallium arsenide, increasing the energy of the waves as they move forward.
“It loses almost 99 percent of its power when going backwards, so we designed it to get a substantial gain forward to beat that,” Wendt said in the release.
The team generated surface waves of around 1 gigahertz – which equates to billions of vibrations per second – and believe the design could be pushed to tens or hundreds of gigahertz. That’s well beyond the capabilities of typical SAW devices, which often reach around 4 GHz, the researchers said.
The long-term goal is to simplify the way phones handle wireless signals, including designing a single chip that can convert radio waves to SAW and vice versa, using surface waves for much of the signal processing. This could potentially allow future wireless devices to filter and route signals on smaller chips, using less power.
“This phonon laser was the last standing domino that we had to knock down,” Wendt added. “Now we can literally make every component you need for a radio on a single chip using the same type of technology.”
