In Brief
- WashU researchers are expanding what photonic chips can do by adding ultrathin crystalline materials as "photonic Legos."
- These ultrathin films can be placed directly wherever their special properties are needed.
- A modular materials framework for photonic circuits could be used for AI systems, photonic computing or quantum technologies.
Most of today's computer chips — also sometimes known as conventional integrated circuits — use electrons to deliver their signals via semiconductor materials and metallic components. In contrast, photonic integrated circuits use faster signal carriers, such as photons or quantized "light particles." Over the past decades, many academic and industry researchers have looked for ways to integrate photonic materials onto chips. By enabling optical links that move data at high speed, these researchers seek to make new kinds of chips for artificial intelligence (AI) systems, photonic computing, co-packaged optics (CPO) and new approaches to sensing and quantum technologies.
However, integrating the desired photonic materials into chip architecture has been the challenge — a challenge that researchers at the McKelvey School of Engineering at Washington University in St. Louis have started to solve.
"We developed a manufacturing process that will give us more freedom to design these new photonic chips," said Sang-Hoon Bae, an assistant professor of mechanical engineering and materials science at McKelvey Engineering. Bae is co-corresponding author of research now published in Nature about a modular materials framework for multifunctional photonic circuits.
Bae's colleague Lan Yang, the Edwin H. & Florence G. Skinner Professor of Electrical and Systems Engineering, is co-lead investigator on the project - and a world-leading expert in integrated photonics.
Bae, a materials scientist, said that he had wanted to collaborate with Yang since before he joined WashU. It has taken years of work, but together their team has found the right process and materials to add new capabilities to photonic chips.
"Silicon photonics gives us a powerful foundation, with decades of investment in chip fabrication and design," Yang said. "Heterogeneous integration lets us build on that foundation while adding materials that can control and detect light in ways silicon alone cannot. That is essential to expanding what integrated photonics can do."
"Using photons for all the best chips is one of the most interesting and fascinating directions for the industry," Bae said. Up until now, the problem has been a materials challenge, he said — that is, finding ideal materials that can integrate with current chip architecture while maximizing photonic integration.
In their new publication, the team detailed how they developed their materials and showcased their uses on the photonics side. "We demonstrate much faster modulation and efficient isolation," Bae said. "We also showcase wide-spectrum light detection, with a full functionality package."
The framework brings new functions and capabilities to established silicon and silicon-nitride photonic chips by transferring ultrathin, freestanding single-crystalline nanomembranes onto prefabricated optical circuits. The WashU researchers avoided known constraints for materials grown directly onto silicon by developing a veritable buffet of ultra-thin films that can be placed directly where their diverse properties — including electrical, magnetic or optical properties — are needed. The frameworks function like photonic Legos, giving tech developers many more options in building the circuits that power the modern world.
"Each material brings its own strengths," Yang said. "By growing high-quality crystals separately and then bringing them onto an existing photonic circuit, we gain more freedom to choose the material for the function we need. We can also combine materials side by side or stack them to bring several functions into one device."
For example:
- Single-crystalline barium titanate (BTO) nanomembranes enable highly efficient electro-optic modulation.
- Cobalt ferrite (CFO) nanomembranes bring nonreciprocal light control to their set of tools.
- Gallium arsenide and gallium nitride membranes were laterally integrated on silicon nitride to detect light at selected wavelengths, from the ultraviolet to the near-infrared, using different devices on the same chip.
- Stacked barium titanate and cobalt ferrite on silicon micro-ring resonators combine electro-optic and magneto-optic functions for multifunctional photonic applications.
And this is just the start, Bae and Yang said. Now, with new ways to bring different functional materials onto the same platform, their work opens the door to many more choices in designing photonic systems. Researchers can build different combinations of materials around each application's needs.
Meng Y et al. Heterogeneous photonic integration of single-crystalline nanomembranes. Nature 657, 638-645 (2026). DOI: https://doi.org/10.1038/s41586-026-11000-w
This work was supported by National Science Foundation (NSF) Program-EPMD (2428676) and a McKelvey Collaboration Initiation Grant to Sang-Hoon Bae and Lan Yang. Bae acknowledges funding support from NSF (2240995, 2329189) and the Air Force Research Laboratory (AFOSR) (FA9550-25-1-0321). WashU postdoctoral research associates Yuan Meng and Wenbo Mao; PhD student Zhihao Xu; and postdoc Di Jia are the co-first authors of this paper.
The experiments were supported by the facilities of the Institute of Materials Science and Engineering (IMSE) at WashU and partly by the Holonyak Micro & Nanotechnology Lab (HMNTL) at the University of Illinois Urbana-Champaign (UIUC).
