Photonic memory

Researchers from the University of Southern California Information Sciences Institute and the University of Wisconsin-Madison fabricated a regenerative photonic latch memory on GlobalFoundries’ commercial silicon photonics platform, a step towards building a complete photonic SRAM system.

The memory cell can store data as light and regenerate the signal to keep it stable against noise. “To fully realize the potential of photonic computing for AI accelerators and tensor cores, we need photonic memory that is just as versatile and robust as its electrical counterparts,” said Ajey P. Jacob, Director of Advanced Electronics at the USC Information Sciences Institute, in a press release. “Our Photonic Latch demonstrates that we can build these essential building blocks using standard, mass-producible manufacturing processes.”

“This work represents a key milestone toward integrated photonic in-memory computing,” added Akhilesh R. Jaiswal, a professor at UW-Madison, in a release. “By demonstrating a cross-coupled differential regenerative architecture, we have shown that it is possible to build scalable, energy-efficient optical memory arrays that can interface directly with future photonic processors.” [1]

Single-photon switch

Researchers from Purdue University demonstrated a photonic switch that operates at single-photon intensities with a nonlinear refractive index several orders of magnitude higher than current best-known materials.

The work uses commercial single-photon avalanche diodes (SPAD), which amplify the effect of a single photon striking silicon to create an electron to create an avalanche effect that generates up to 1 million new electrons. “This multiplication is a very powerful tool for connecting the microscopic quantum world with the macroscopic world,” said Demid Sychev, a postdoctoral researcher in the Elmore Family School of Electrical and Computer Engineering at Purdue, in a press release. “This principle was often used for single-photon detection, but what we did was apply this process to create a huge nonlinearity for optical beams, where one single-photon beam can control a huge macroscopic beam.”

The device functions as an optical switch, where a single photon in the control beam can modulate the properties of a more powerful probe beam, effectively switching it on or off. Compatible with CMOS, it can operate at room temperature at gigahertz speeds, with te potential to reach hundreds of gigahertz.

“The reason why a photonic computer is not realized is because the current approaches using photons are supposed to be much better. Photons consume less energy; they are faster. Ideally, from photons, you can get terahertz clock rates of CPUs, compared to currently existing 5 gigahertz in the best cases. But the problem is that there are no photonic switches like this. The needed interaction between photons typically requires high powers of optical light. With our method, in principle, you can do it with single photons,” Sychev continued. “Previously, all commercially available SPADs we used were not designed for this purpose. Now our goal is to make a device which will be optimized to work as a single-photon switch.” [2]

Slow light

Researchers from the University of Illinois Urbana-Champaign Grainger College of Engineering developed a technique to slow light on photonic chips and enable resonators to hold light longer by using spectral hole burning combined with an erbium-doped lithium niobate platform that provided tunability over a large bandwidth.

“One of the most efficient ways to store light is by slowing it down,” said Elizabeth Goldschmidt, an associate professor of physics at the University of Illinois Urbana-Champaign, in a statement. “Slowing the propagation acts like storage: if you make a long path and slow it down, it lives there for a while.”

The team initially used spectral hole burning on a resonator in an attempt to make more efficient quantum memories. “I was seeing an unexpected dip during our scan, which didn’t make sense. We eventually concluded that this dip was caused by the slow-light effect,” said Priyash Barya, a graduate student in the Department of Electrical and Computer Engineering at the University of Illinois Urbana-Champaign, in a statement. “Normally you make a device with the intention of doing one thing, and if you want to do something different, you have to make a new device. But because we’re using spectral hole burning to give the device its properties, we can reconfigure as often as we want, over and over again.”

“We think this platform can be used for all sorts of things, like quantum memory on-chip, slowing down single photons in order to store them, and making more exotic structures on-chip by doing things more complicated that just burning single spectral holes,” added Goldschmidt. “We’re a hammer looking for nails, and we’ve already found a lot.” [3]

References

[1] Md. Abdullah-Al Kaiser, S. Sunder, A. Jaiswal, A. Jacob. Demonstration of a Cross-Coupled Differential Regenerative Photonic Latch for Integrated Ultra-fast On-Chip Memory. IEEE IEDM 2025. https://iedm25.mapyourshow.com/8_0/sessions/session-details.cfm?scheduleid=146

[2] D.V. Sychev, P. Chen, Y. Chen, et al. All-optical modulation with single photons using an electron avalanche. Nat. Nanotechnol. (2025). https://doi.org/10.1038/s41565-025-02056-2

[3] P. Barya, A. Prabhu, L. Heller, et al. Ultra high-Q tunable microring resonators enabled by slow light. Nat Commun 16, 10496 (2025). https://doi.org/10.1038/s41467-025-65533-1

Jesse Allen

(all posts) Jesse Allen is the Knowledge Center administrator and a senior editor at Semiconductor Engineering.