Addressing a major roadblock in next-generation photonic computing and signal processing systems, 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 analog light signals in one fluid step. Built on chips made out of lithium niobate, the device offers a potential replacement for the ubiquitous but energy-intensive digital-to-analog 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, rely on conversion of massive amounts of data between the electrical domain – used for storage and computation — and the optical domain — used for data transfer,” said senior author Marko Loncar, 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-analog converters, followed by electro-optic modulators, accomplish the task of converting digital electronic signals into analog photonic signals, a process that underpins modern transceiver systems in data centers. But this workflow is often complex, multi-tiered, and can be energy-intensive. An artist’s depiction of the electro-optic digital-to-analog converter, depicting high-speed information transfer between electronics and optics. Courtesy of Second Bay Studios/Harvard SEAS. “When you’re computing with light, all the energy that you’ve saving, all the speed that you’re getting, tends to be offset by these big, expensive, inefficient electronic boxes that you need in order to take zeros and ones and turn them into a sine wave, square wave, triangle wave, or any meaningful waveform,” said co-first author Yunxiang Song, graduate student in the Loncar Lab. “These things are actually the bottleneck in many types of photonic computing … So the question was, can we design some kind of novel photonic modulator that obviates the need for these electronic digital-to-analog converters?” The developed device offers just that: Using the efficient electro-optic properties of thin-film lithium niobate, it can turn purely digital electronic inputs into analog optical signals at information rates reaching up to 186 Gb/s — an order of magnitude faster than typical home internet speeds. 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. Additionally, the work comes at a time when emerging optical computing approaches, or computing using light rather than electrons, are of great interest: Photons have the potential to process data in parallel and more efficiently than conventional electronics. “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, the researchers 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, that mirrors what exists for silicon chips. In doing so, the team showed not only that the device works for its particular application, but also that the device can be made in a high-volume and low-cost manner — further paving the way for novel photonic technologies that can complement silicon photonics. The research was published in Nature Photonics (www.doi.org/10.1038/s41566-025-01719-9).