Breaking the Size-Speed Barrier in Photonic Switching

In a new study published in Nature Photonics , researchers from the University of Pennsylvania School of Engineering and Applied Science (Penn Engineering) describe the development of a new photonic switch that solves the size-speed tradeoff. The new switch unit measures 85 x 85 micrometers, smaller than a grain of salt.

From left: Professor Liang Feng and team members Xilin Feng, Tianwei Wu, and Shuang Wu. — *From left, Professor Liang Feng with team members Xilin Feng, Tianwei Wu and Shuang Wu. Image credit: Bella Siervo*

Every second, terabytes of data (the equivalent of downloading thousands of movies at once) travel around the world in the form of light on fiber optic connections. Once that information reaches a data center, a switching mechanism is required.

Until now, photonic switches used to route optical signals have been hampered by a fundamental trade-off between size and speed: larger switches can process more data at higher speeds, but they also consume more power, take up more physical space and are more expensive.

Accelerating the Information Superhighway

By manipulating light at the nanoscale with incredible efficiency, the new switch could speed up data transmission on the world’s fiber-optic information superhighway.

This could speed up everything from streaming movies to AI training.

Liang Feng, senior study author and professor in the Department of Materials Science and Engineering at the University of Pennsylvania

Fusion of quantum mechanics and optics

The new switch is based on non-Hermitian physics, a branch of quantum mechanics that studies how some systems behave in peculiar ways, giving researchers greater control over the behavior of light.

The gain and attenuation of the material can be adjusted to direct the optical signal to the correct output on the communication line.

Xilin Feng, a doctoral student in the Department of Electrical Systems Engineering at the University of Pennsylvania and lead author of the study

In other words, researchers can use unique physics to manage the flow of light on a tiny chip, giving them precise control over the connectivity of any light-based network.

This revolutionary switch can redirect signals in trillionths of a second while using minimal power.

This speed is approximately one billion times faster than the blink of an eye. Until now, switches have been either small or fast, but achieving both properties at the same time has been extremely difficult.

Shuang Wu, co-author, doctoral candidate at the University of Pennsylvania

Scaling up with silicon

Most importantly, the new switches are made in part from silicone, an industry-standard material that is both affordable and readily available.

“Non-Hermitian switching techniques have never been demonstrated on a silicon photonic platform before, ” Wu added.

In theory, adding silicon to the switch would make the device easier to scale for mass production and widespread industrial use. Silicon is a key building block of most technologies, from computers to smartphones.

The device’s silicon architecture ensures compatibility with existing silicon photonic foundries that manufacture advanced devices such as graphics processing units (GPUs).

From concept to prototype

The switch consists of indium gallium arsenide phosphate (InGaAsP) on a layer of silicon, a semiconductor material that is particularly effective at controlling light in the infrared wavelengths commonly transmitted in undersea fiber optic cables.

Combining these two layers proved to be very challenging and required a lot of effort to create a workable prototype.

“The alignment requires nanometer precision,” Wu noted.

Data Center Migration

The researchers argue that the new switch will benefit not only academic physicists, who will be able to continue their research into the non-Hermitian physics that underpins the switch, but also the companies that manage and develop data centers and the billions of users that rely on them.

” Data can only travel as fast as we can control it,” Liang Feng said. ” And our experiments have demonstrated that the speed limit of our system is just 100 picoseconds. “

This research was conducted at the University of Pennsylvania’s School of Engineering and Applied Science. This research was funded by the Army Research Office (ARO) (W911NF-21-1-0148 and W911NF-22-1-0140), the Office of Naval Research (ONR) (N00014-23-1-2882), and the National Science Foundation (NSF) (ECCS-2023780, DMR-2326698, DMR-2326699, and DMR-2117775).

Tianwei Wu, Zihe Gao, Haoqi Zhao and Yichi Zhang of Pennsylvania Institute of Technology and Li Ge of the City University of New York are co-authors on the study.