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 novel photonic switch that solves the size-speed tradeoff. The new switch’s units measure 85 by 85 micrometers, making them smaller than a grain of salt.
Professor Liang Feng and group members Xilin Feng, Tianwei Wu and Shuang Wu, from left. Image Credit: Bella Ciervo
Every second, terabytes of data—the equivalent of downloading thousands of movies at once—travel around the world as light in fiber-optic connections. When the information reaches data centers, it requires a switching mechanism.
Until now, photonic switches used for routing optical signals have been hampered by a fundamental tradeoff between size and speed: larger switches can handle faster speeds and more data, but they also consume more energy, take up more physical space, and increase prices.
Speeding Up the Information Superhighway
By manipulating light at the nanoscale with remarkable efficiency, the new switch accelerates transferring data on and off the world's literal information superhighway of fiber-optic cables.
This has the potential to accelerate everything from streaming movies to training AI.
Liang Feng, Study Senior Author and Professor, Materials Science and Engineering, University of Pennsylvania
Quantum Mechanics Meets Optics
The new switch is based on non-Hermitian physics, a branch of quantum mechanics that studies how certain systems behave in unique ways, offering researchers greater control over light’s behavior.
We can tune the gain and loss of the material to guide the optical signal towards the right information highway exit.
Xilin Feng, Study First Author and Doctoral Student, Electrical and Systems Engineering, University of Pennsylvania
In other words, the researchers can use the unique physics at work to manage the flow of light on the tiny chip, giving them precise control over the connection of any light-based network.
The innovative switch can redirect signals in trillionths of a second while using minimal power.
This is about a billion times faster than the blink of an eye. Previous switches were either small or fast, but it’s very, very difficult to achieve these two properties simultaneously.
Shuang Wu, Study Co-Author and Doctoral Student, University of Pennsylvania
Using Silicon for Scalability
The novel switch is particularly significant because it is partially manufactured from silicon, an affordable and easily accessible industry standard material.
Wu added, “Non-Hermitian switching has never been demonstrated in a silicon photonics platform before.”
Theoretically, adding silicon to the switch will make it easier to scale the device for mass production and widespread industrial use. Silicon is a crucial component of most technologies, from computers to smartphones.
The device’s silicon construction ensures compatibility with current silicon photonic foundries, which produce advanced devices such as graphics processing units (GPUs).
From Concept to Prototype
The switch is composed of indium gallium arsenide phosphate (InGaAsP) on top of the silicon layer. This semiconductor material is particularly adept at controlling infrared light wavelengths, such as those usually transmitted in undersea optical cables.
Joining the two layers proved difficult, requiring multiple efforts to create a workable prototype.
Wu noted, “The alignment requires nanometer accuracy.”
Transforming Data Centers
The researchers claim that the novel switch will help academic physicists, who can now further investigate the non-Hermitian physics on which it is based, and companies that manage and develop data centers and the billions of users who rely on them.
Liang Feng stated, “Data can only go as fast as we can control it. And in our experiments we showed that the speed limit of our system is just 100 picoseconds.”
This research was carried out at the University of Pennsylvania School of Engineering and Applied Science. It 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 Penn Engineering and Li Ge of the City University of New York are the other study co-authors.
Journal Reference:
Feng, X., et. al. (2024) Non-Hermitian hybrid silicon photonic switching. Nature Photonics. doi.org/10.1038/s41566-024-01579-9