Digital to analogue in one smooth step
Researchers in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have created a device that can bridge digital electronic signals and analogue light signals in one fluid step. The research is published in Nature Photonics.
Built on chips made out of lithium niobate, the new device, they say, offers a potential replacement for the ubiquitous but energy-intensive digital-to-analogue conversion and electro-optic modulation systems used all over today’s high-speed data networks.
“Optical communication and high-performance computing, including large language models, relies on conversion of massive amount of data between the electrical domain – used for storage and computation – and the optical domain – used for data transfer,” said senior author Marko Lončar, the Tiantsai Lin Professor of Electrical Engineering at SEAS .“For photonic technologies to seamlessly integrate with electronic ones, the interfaces between them must be fast and energy-efficient.”
Today, electronic digital-to-analogue converters, followed by electro-optic modulators, accomplish the task of converting digital electronic signals into analogue photonic signals, a process that underpins modern transceiver systems in data centres. But such a workflow is often complex, multi-tiered, and can be energy-intensive.
The new Harvard device makes use of the efficient electro-optic properties of thin-film lithium niobate to turn purely digital electronic inputs into analogue optical signals at information rates reaching up to 186 gigabits per second. The device could also enable advances in microwave photonics, for example in wireless or radar communications, as it can be combined with photodetection to perform optical-to-electronic conversion for creating radio frequency signals.
“Our work has the potential to address the current bottleneck of computing and data interconnects particularly in AI technologies,” said co-first author Yaowen Hu, former postdoctoral researcher at Harvard SEAS and now assistant professor at Peking University.
To demonstrate that their device handles data with precision and speed, they tested it by optically encoding images from the well-known MNIST dataset, typically used to benchmark photonic computing systems.
The researchers’ device was fabricated using a lithium niobate foundry process developed by Harvard startup HyperLight Corporation.
