Sound bends light on a tiny chip

New University research involving computer chips could eventually help bolster wireless computing speeds.

Parker Lemke

Developmental computer chip technology engineered by University of Minnesota researchers could someday boost wireless communication speeds and aid scientists studying quantum physics.

The researchers created a single chip that generates and contains both sound and light waves, the first of which modulates the optical light waves used to carry information, said lead researcher and physics doctoral student Semere Tadesse.

The sound vibrations, generated like earthquake waves on the surface of the chip, alter the properties of the chip’s materials, Tadesse said. The light waves pass through the chip materials.

By modulating the light at a faster rate, researchers were able to increase the device’s capacity to carry information.

“We effectively bend the light,” Tadesse said.

The chip technology research, which was funded by the National Science Foundation and the Air Force Office of Scientific Research, was published in November.

The team used electron beams and nanofabrication techniques to create nanoscale transducers small enough to excite the sound waves at high frequencies, said electrical and computer engineering assistant professor Mo Li, who serves as Tadesse’s adviser.

“The higher the frequency, the smaller [and] finer the transducer has to be,” Li said, adding that the technology used is still budding.

Scientists have explored controlling light waves with sound vibrations for decades, Tadesse said, but they were always limited by bulky materials and slow modulation speeds.

In order to efficiently control the light waves, the researchers integrated optical circuits and acoustic devices on a single chip, Tadesse said.

“Everything is all about miniaturization,” he said. “You really want to have almost every functionality on the same device.”

Optical technology already forms the backbone of the Internet, said electrical and computer engineering professor James Leger, and it was first used to connect computers across continents.

Now, the use of optical communication within computers or even chips is seen as a way to significantly boost their speed, he said. Unlike electronic signals, optical beams don’t disrupt each other when they cross, he said, which allows many signals to run simultaneously.

To harness optical technology for communication and computing, the chip must modulate the light wave by turning it on and off at rapid speeds, Leger said.

Transmitting signals with optical beams is more favorable than using a wire, he said, but getting modulators to work at such high frequencies is difficult in small devices.

The device Li and Tadesse worked on could help quicken modulation speeds, he said.

“You can turn it on and off tens of billions of times a second to send your information,” he said.

Tadesse is working to push that frequency even higher, Li said.

“Right now, we are [at] about 10 gigahertz,” Li said. “We want to push to 20 to 25 gigahertz.”

Tadesse said he and Li will also continue hunting for new applications for the technology.

“He shows me the general directions, and then I do the work,” Tadesse said. “There’s a lot of feedback between us.”