Researchers merge light and sound on microchips, unlocking a new frontier in data processing, sensing, and communication.

Microchips have always relied on electricity to process data, but what if they could harness sound instead? In a groundbreaking twist, researchers have managed to confine high-frequency sound waves to a chip's surface that ripple like a miniature earthquake – an unexpected breakthrough that could redefine everything from data processing to advanced sensing, signaling a seismic shift in how we sense and share data.

For decades, microchips have been the bedrock of modern technology, translating electrical signals into the data that powers everything from smartphones to supercomputers.

Since their inception, traditional microchips have relied on electricity to power hardware and bring software to life. This rigid system remains bound to meticulously engineered circuits and pathways to move electrons that result in heat generation and energy loss – issues that have become increasingly difficult to manage as components shrink.

But as demand for faster, more efficient devices grows, so does the need for a new kind of chip – one that can handle more data without the heat and energy drain of traditional circuits. That's where an unexpected player comes in – sound.

At the University of Sydney, researchers have been pushing the boundaries of microchip technology, seeking to move beyond the limitations of electron-based designs. Their efforts have culminated in a pioneering technique that integrates high-frequency sound waves directly onto the chip's surface, setting a new precedent for what microchips can achieve.

Instead of needing a rigid system, sound functions as both an electrical conduit and transmitter – moving energy through vibrations within a material and adapting naturally to its environment.

On a microchip, these high-frequency sound waves can be confined to the surface, providing a more flexible and efficient way to transmit data without the losses of traditional designs.

Redefining microchips

This innovative use of sound marks a significant leap in microchip design and, by proxy, all technologies that use microchips.

By harnessing this fundamental function, researchers have used lasers to generate high-frequency sound waves on the chip's surface, creating a new mode of data transmission that works with the natural behavior of energy itself, bypassing the constraints of electron flow.

The researchers demonstrated that this method goes beyond merely confining sound waves; it facilitates direct interaction with light signals on the chip's surface – a breakthrough that could reshape technologies such as medical imaging devices that provide clearer diagnostic images, smart thermostats that optimize energy efficiency, advanced smoke detectors capable of distinguishing smoke types, and cutting-edge smartphones that leverage more advanced frequencies.

By redefining core electronic design, this advancement promises to deliver more efficient and versatile devices across a wide range of critical applications.

The University of Sydney

From left to right: Lead author Choon-Kong Lai, research lead Moritz Merklein and Ben Eggleton with the new chip in the laboratories of the Sydney Nanoscience Hub.

"The use of sound waves on the surface of a microchip has application in sensing, signal processing and advanced communications technology," said senior author and project lead Moritz Merklein from the University of Sydney Nano Institute and School of Physics. "We can now start to think about new designs for chips that use light and sound instead of electricity."

Lead author Govert Neijts, a student from the University of Twente in the Netherlands who spent nine months at the University of Sydney labs, highlighted the innovative shift in how sound waves are generated on the chip.

"Typically, surface acoustic waves are 'excited' using electronics. Here we use photonics, or light energy, to produce the sound wave," he explained. "This approach has multiple advantages, chief of which is that light does not produce the heat in the chip that electronic excitation causes."

Just as the vibrations of an earthquake can travel great distances, the integration of high-frequency sound waves with light signals demonstrates a novel path forward, translating the power of this technology into applications that were previously constrained by traditional designs.

Nevertheless, this groundbreaking approach not only enhances efficiency but also showcases the potential of advanced materials in redefining microchip technology.

Special glass

To achieve this novel integration of light and sound, researchers employed the critical minerals germanium and arsenic, as well as the compound selenide, which were chosen for their favorable properties in electronic applications.

Valued for its high electron mobility, germanium has been increasingly explored as a semiconductor material in various applications, particularly in high-speed electronic devices and photonic systems.

Its ability to efficiently conduct electricity makes it a suitable choice for enhancing the performance of microchips.

Known more widely as a highly toxic element, arsenic actually has numerous roles that are often overshadowed by its harmful effects.

In the realm of electronics, arsenic is primarily used in semiconductor alloys, where it enhances the performance of materials like gallium arsenide. Its presence improves electron mobility and contributes to the efficiency of electronic devices, making it a valuable component in microchip design.

Selenium, often recognized for its role in various industrial applications, is valued for its unique conductive properties. This element is particularly effective in photoconductors and solar cells, enhancing light absorption and facilitating efficient energy transfer.

When combined with germanium and arsenic, selenium forms a compound that enhances the semiconductor properties of the microchip and plays a crucial role in improving performance, making it essential in the innovative integration of light and sound.

Utilizing these elements, the researchers developed a unique glass known as GeAsSe (germanium-arsenic-selenide) to serve as an effective "wave guide." This material not only facilitates the efficient propagation of high-frequency sound waves but also enhances interactions between light and sound, creating an optimal environment for energy transmission.

"The material is considered a soft glass," said Merklein. "This means that unlike many materials, it operates as a guide for the high-frequency sound waves and lets them more freely interact with the light waves we put into the chip."

By harnessing the properties of GeAsSe, the research team has opened new avenues for microchip design, enabling more compact and efficient devices capable of advanced functionalities.

"Imagine sensors that can detect minute changes in the environment or advanced signal processing techniques that enhance communication technologies," said co-author Choon-Kong Lai, a postdoctoral researcher at the Institute of Photonics and Optical Science at the University of Sydney. "Our innovative approach not only paves the way for more sensitive and efficient devices but also expands the potential for integrating acoustic and optical technologies on a single chip."

Sound of light

Building off another world's first achievement of converting optical data into acoustic information on a microchip – an innovation dubbed as "storing lightning inside thunder" – the researchers have further advanced their understanding of the interplay between light and sound.

To realize this latest breakthrough, the team employed a technique known as stimulated Brillouin scattering (SBS), a process where light generates sound waves within a medium, creating a feedback loop that enhances their interaction.

Essentially, this phenomenon allows photons (light) and phonons (sound) to couple more efficiently, maximizing and enabling a new way to transfer energy on a microchip.

As light travels through the chip or an optical fiber, it generates sound vibrations – previously considered a hindrance in optical communications. However, by leveraging SBS, the researchers managed to couple and amplify these vibrations, transforming them from a nuisance into a powerful tool for transporting and processing information on the chip.

"We have developed this work to be able to manage and guide high-frequency sound wave information on the surface of a chip," said co-author and research team leader, Ben Eggleton, pro-vice-chancellor (research) at the University of Sydney, "This is an important contribution for the development of emergent sensing technologies."

This ability to manage high-frequency sound waves on a chip marks a pivotal advancement not only in sensing technology, enhancing both data processing and signal detection, but also in any technology that relies on precise energy transference.

By enabling more exacting control of high-frequency sound waves on microchips, this discovery opens the door for a new era of devices that are not only more efficient but also capable of unprecedented sensitivity – potentially redefining information processing, transmission, and detection, setting a new standard for future technologies that integrate both light and sound.