WashU Researchers Develop Modular Framework for Advanced Photonic Circuits

We developed a manufacturing process that will give us more freedom to design these new photonic chips, said Sang-Hoon Bae. Published in Nature, a team at Washington University in St. Louis has developed a modular materials framework for advanced photonic circuits that allows scientists to transfer freestanding single-crystalline nanomembranes onto prefabricated optical circuits, enabling faster modulation, wide-spectrum light detection, and multifunctional applications on silicon and silicon-nitride chips.

Conventional computer chips rely on electrons traveling through semiconductor materials and metallic components to carry signals. Photonic integrated circuits, by contrast, utilize faster signal carriers like photons or quantized light particles. For decades, researchers have examined ways to integrate photonic materials onto chips to support artificial intelligence systems, photonic computing, co-packaged optics, and advancements in sensing and quantum technologies.

Washington University Team Introduces Fabrication Process

A team at the McKelvey School of Engineering at Washington University in St. Louis has introduced a process to address this hurdle. Bae serves as an assistant professor of mechanical engineering and materials science at McKelvey Engineering and co-corresponding author of the research.

Bae collaborated with Lan Yang, the Edwin H. & Florence G. Skinner Professor of Electrical and Systems Engineering and an expert in integrated photonics, who served as co-lead investigator on the project. While silicon photonics provides a baseline with established fabrication and design methods, Yang noted that heterogeneous integration allows researchers to incorporate materials capable of controlling and detecting light beyond what silicon can achieve alone.

WashU Researchers Develop Modular Framework for Advanced Photonic Circuits

Researchers Deploy Ultra-Thin Films as Modular Building Blocks

Instead of growing materials directly onto silicon, the team developed a collection of ultra-thin films that can be positioned precisely where their optical, electrical, or magnetic properties are required. The framework functions similarly to modular building blocks.

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.

Engineers Detail Material Combinations on Standard Chip Platforms

The research details specific material combinations engineered onto standard chip platforms:

Single-crystalline barium titanate (BTO) nanomembranes provide highly efficient electro-optic modulation.
Cobalt ferrite (CFO) nanomembranes introduce nonreciprocal light control tools.
Gallium arsenide and gallium nitride membranes were integrated laterally on silicon nitride to enable light detection across selected wavelengths from the ultraviolet to the near-infrared on a single device.
Stacked barium titanate and cobalt ferrite placed on silicon micro-ring resonators merge electro-optic and magneto-optic functions into multifunctional applications.

Framework Enables Tailored Photonic Systems for Specific Requirements

We also showcase wide-spectrum light detection, with a full functionality package.

By enabling developers to mix and match functional materials on established silicon and silicon-nitride platforms, the framework offers new pathways for tailoring photonic systems to specific application requirements.