Bringing electronics and photonics together: Co-packaged optics, hybrid SoC, and CSiGeSn alloy.
Researchers from the Massachusetts Institute of Technology (MIT) and Bridgewater State University developed a new way to co-package photonic and electronic chips that uses existing automated pick-and-place assembly equipment in traditional fabs along with a less-expensive passive alignment process.
“We’ve developed a packaging design [for integrating photonics with electronics] that is reliable, has a larger alignment tolerance, doesn’t lose much light, and doesn’t waste too much space. Basically, it has all the features you want for an efficient and functional interconnect,” said Luigi Ranno, a graduate student in MIT’s Department of Materials Science and Engineering, in a statement.
The method uses a vertical chip-to-chip evanescent coupler between silicon and silicon nitride. In tests, it demonstrated 90% coupling efficiency near telecommunication wavelengths and micron-scale alignment tolerances. “Conventional couplers have a single coupling point, making alignment tolerances very tight. But our new coupler has a much larger interaction length, increasing the alignment tolerance,” said Anu Agarwal, principal research scientist at MIT’s Materials Research Laboratory and head of the FUTUR-IC research team, in a statement. The coupler can also transmit light vertically between stacked chips. [1]
Researchers from Boston University, UC Berkeley, and Northwestern University fabricated an electronic–photonic–quantum system-on-chip in a commercial foundry. The SoC combines quantum light sources and stabilizing electronics to produce reliable streams of correlated photon pairs for quantum computing. It was fabricated using a standard 45nm CMOS manufacturing process developed in collaboration with GlobalFoundries and Ayar Labs.
“Quantum experiments in the lab usually need big, bulky equipment, which requires pristine, clean conditions,” said Anirudh Ramesh, a PhD student at Northwestern, in a press release. “We took many of those electronics and shrunk them down onto one chip. So, now we have a chip with built-in electronic control — stabilizing a quantum process in real time. This is a key step toward scalable quantum photonic systems.”
Twelve silicon microring resonators per chip are used to generate the streams of correlated photons. To keep the twelve sources operating in parallel, each resonator must stay in sync with its incoming laser light even in the presence of temperature drift and interference from nearby devices. To address this, the team integrated photodiodes inside the resonators to monitor the alignment with the incoming laser. They also added on-chip heaters and control logic to continually adjust the resonance in response to drift.
In addition to computing, the researchers see potential applications in sensing and communications. [2]
Researchers from Forschungszentrum Jülich and the Leibniz Institute for Innovative Microelectronics developed a stable alloy of carbon, silicon, germanium, and tin with applications in electronics, photonics, and quantum technology.
All four elements of the CSiGeSn alloy are part of Group IV, making it compatible with CMOS processing. The alloy makes it possible to fine-tune the material’s structural and electrical properties, enabling the creation of optical components or quantum circuits that could be integrated directly onto a chip during manufacturing.
Researchers have previously combined silicon, germanium, and tin to develop transistors, photodetectors, lasers, LEDs, and thermoelectrics. Key to the new alloy is the addition of carbon, which provides greater control over the band gap. Integrating the carbon, however, was challenging due to the difference in size and bonding force between it and tin. This was overcome through precise tuning of an industrial CVD system and use of CBr4 as a precursor.
“By combining these four elements, we have achieved a long-standing goal: the ultimate Group IV semiconductor,” said Dan Buca, a group leader in the Peter Grünberg Institute at Forschungszentrum Jülich, in a statement. He noted several potential applications: “An example is a laser that also works at room temperature. Many optical applications from the silicon group are still in their infancy. There are also new opportunities for the development of suitable thermoelectrics to convert heat into electrical energy in wearables and computer chips.” [3]
[1] D. Weninger, S. Serna, L. Ranno, et al. Low Loss Chip-to-Chip Couplers for High-Density Co-Packaged Optics. Adv. Eng. Mater., 27: 2402095. https://doi.org/10.1002/adem.202402095
[2] D. Kramnik, I. Wang, A. Ramesh, et al. Scalable feedback stabilization of quantum light sources on a CMOS chip. Nat Electron 8, 620–630 (2025). https://doi.org/10.1038/s41928-025-01410-5
[3] O. Concepción, A. J. Devaiya, M. H. Zoellner, et al. Adaptive Epitaxy of C-Si-Ge-Sn: Customizable Bulk and Quantum Structures. Adv. Mater. 2025, 2506919. https://doi.org/10.1002/adma.202506919
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