This image visualizes the design of a heterogeneous integrated photonic chip incorporating various functional single-crystalline nanomembranes. These ultrathin layers add capabilities that the underlying chip materials alone cannot provide. Researchers at WashU have developed a new framework to expand the materials, functions and designs on a single chip, opening new possibilities for faster, more powerful and multifunctional photonic technologies.
Image Credit: AI generated, courtesy of Bae lab
Scientific Frontline: Extended "At a Glance" Summary: Heterogeneous Photonic Integration
The Core Concept: A manufacturing framework that integrates diverse functional materials onto single photonic chips by transferring ultrathin, single-crystalline nanomembranes onto prefabricated optical circuits.
Key Distinction/Mechanism: Unlike conventional chips that use electrons to deliver signals, photonic chips use photons, enabling faster optical links. This specific method avoids the constraints of growing materials directly on silicon by instead building separate high-quality crystals and placing them as ultrathin films ("photonic Legos") onto existing photonic circuits.
Major Frameworks/Components:
- Barium titanate (BTO) nanomembranes for electro-optic modulation.
- Cobalt ferrite (CFO) nanomembranes for nonreciprocal light control.
- Gallium arsenide and gallium nitride membranes integrated laterally on silicon nitride for wide-spectrum light detection (ultraviolet to near-infrared).
- Stacked barium titanate and cobalt ferrite on silicon micro-ring resonators to combine electro-optic and magneto-optic functions.
Branch of Science: Materials Science, Photonics, Electrical and Systems Engineering.
Future Application: Advanced photonic chips for artificial intelligence (AI) systems, photonic computing, co-packaged optics (CPO), quantum technologies, and high-speed sensing.
Why It Matters: It solves a major materials challenge by allowing engineers to combine multiple specialized materials onto a single chip architecture, maximizing photonic integration and enabling faster, more powerful, and multifunctional computing capabilities.
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 a co-corresponding author of the research, which was recently published in Nature, detailing 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 a 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 ultrathin 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 microring 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.
Funding: This work was supported by the 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 the NSF (2240995, 2329189) and the Air Force Office of Scientific Research (AFOSR) (FA9550-25-1-0321).
Published in journal: Nature
Title: Heterogeneous photonic integration of single-crystalline nanomembranes
Authors: Yuan Meng, Wenbo Mao, Zhihao Xu, Di Jia, Mengxin Lin, Jisung Seo, Bora Kim, Xinyuan Zhang, Eugene Park, Seokje Lee, Jekyung Kim, Sangmoon Han, Ji-Yun Moon, Weijie Xu, Qian Zhang, Xiaoqing He, Mingfeng Chen, Sang Hyun Nam, Jianqi Hu, Justin S. Kim, Sejin Lee, Sanggeun Bae, Soo Ho Choi, Tae Hyung Kim, Yunseok Choi, Seung-Il Kim, Kyubeen Kim, Minho Jin, Chen Jiang, Yiheng Zhang, Young-Hoon Kim, Jae-Hyun Lee, Hobeom Kim, Sheng Ran, Xi Wang, Cheng-Wei Qiu, Frances M. Ross, Jeehwan Kim, Minjoo Larry Lee, Hyunseok Kim, Tobias J. Kippenberg, Lan Yang, and Sang-Hoon Bae
Source/Credit: Washington University in St. Louis | Leah Shaffer
Edited by: Scientific Frontline
Reference Number: ms100726_01
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