In a recent study published in Nature Photonics, a research team led by Lawrence Berkeley National Laboratory (Berkeley Lab), Columbia University, and Universidad Autónoma de Madrid developed a new optical computing material using photon avalanching nanoparticles.
The accomplishment enables the development of nanometer-scale optical memory and transistors, similar to current microelectronics technology. Using an optical phenomenon called “intrinsic optical bistability,” this approach could lead to smaller and faster components for next-generation computers.
This is the first practical demonstration of intrinsic optical bistability in nanoscale materials. The fact that we can reproducibly make these materials and understand their unintuitive properties is critical for making optical computers at scale a reality.
Emory Chan, Study Co-Lead Author and Staff Scientist, Molecular Foundry, Lawrence Berkeley National Laboratory
The research is part of Berkeley Lab’s broader effort to develop smaller, faster, and more energy-efficient microelectronics using novel materials and processes.
For decades, researchers have aimed to create a computer that uses light instead of electricity. Materials with intrinsic optical bistability (IOB), which allows a material to switch between two different states using light, could be components for optical computers.
In previous studies, optical bistability was mostly found in bulk materials that were too large for microprocessors and difficult to mass produce. In the few studies of nanoscale IOB, the process was poorly understood and assumed to occur through heating the nanoparticles, which is inefficient and hard to control.
However, Chan and colleagues’ recent study suggests that the novel photon avalanching nanoparticles may overcome these challenges for implementing IOB at the nanoscale.
At Berkeley Lab’s Molecular Foundry, a nanoscale scientific user facility, the researchers created 30-nanometer nanoparticles from a potassium-lead-halide material doped with neodymium, a rare-earth element used in lasers.
When the nanoparticles were excited by light from an infrared laser, they exhibited a phenomenon known as “photon avalanching,” where a small increase in laser power results in a large, disproportionate rise in the light emitted by the nanoparticles.
The researchers first identified this “extreme nonlinearity” of photon avalanching nanoparticles in their 2021 publication, which showed that doubling the laser power increased the emitted light intensity by 10,000 times.
In their most recent study, the team found that the new nanoparticles were nearly three times more nonlinear than the original avalanching nanoparticles, representing “the highest nonlinearities that anyone has ever observed in a material.”
Additional experiments revealed that these nanoparticles only completely shut off at very low laser powers. They also continued to emit light brightly, even when the laser power was reduced below the threshold that typically triggers photon avalanching, showing that the IOB previously puzzling to nanoscientists was caused by these tiny avalanching nanoparticles.
According to Chan, there are intermediate laser power levels at which the nanoparticles can be either bright or dark, depending on their previous state, due to the significant difference between the “on” and “off” threshold levels. This behavior suggests that the nanoparticles could serve as nanoscale optical memory, potentially for volatile random-access memory (RAM), by altering optical characteristics without modifying the material.
The researchers used computer models to demonstrate for the first time that the IOB in their nanoparticles results not from heating but from the extreme nonlinearity of photon avalanching and a unique structure that dampens vibrations in the particles. This was done to understand the origins of the bistability in these materials.
Future research will focus on developing new nanoparticle formulations with enhanced optical bistability and environmental stability, as well as exploring additional applications for optically bistable nanomaterials.
Berkeley Lab’s Molecular Foundry is a user facility for nanoscale science.
The study was funded by the Office of Science of the Department of Energy, with additional support from the National Science Foundation and the Defense Advanced Research Projects Agency (DARPA).
Journal Reference:
Skripka, A. et. al. (2025) Intrinsic optical bistability of photon avalanching nanocrystals. Nature Photonics. doi.org/10.1038/s41566-024-01577-x
