OSU researchers investigate new nanocrystals

"The extraordinary switching and memory capabilities of these nanocrystals may one day become integral to optical computing -- a way to rapidly process and store information using light particles, which travel faster than anything in the universe," explained Artiom Skripka, Assistant Professor in the OSU College of Science. "Our findings have the potential to advance artificial intelligence and information technologies generally."

The study, which involved Skripka and collaborators from Lawrence Berkeley National Laboratory, Columbia University and the Autonomous University of Madrid, looked at a type of material called avalanching nanoparticles.

Nanomaterials are small bits of matter measuring at one-billionth and one-hundred-billionths of a meter, while avalanching nanoparticles feature extreme non-linearity in their light-emission properties; meaning they emit light whose intensity can increase significantly with a small increase in the intensity of the laser that’s exciting them. 

The research studied nanocrystals composed of potassium, chlorine and lead and doped with neodymium. The potassium lead chloride nanocrystals don’t interact with light on their own but as hosts they can enable their neodymium guest ions to handle light more efficiently which makes them useful for optoelectronics, laser technology and other optical applications.

"Normally, luminescent materials give off light when they are excited by a laser and remain dark when they are not," said Skripka. "In contrast, we were surprised to find that our nanocrystals live parallel lives. Under certain conditions, they show a peculiar behaviour: They can be either bright or dark under exactly the same laser excitation wavelength and power.

"If the crystals are dark to start with, we need a higher laser power to switch them on and observe emission, but once they emit, they remain emitting and we can observe their emission at lower laser powers than we needed to switch them on initially,” Skripka continued. “It's like riding a bike -- to get it going, you have to push the pedals hard, but once it is in motion, you need less effort to keep it going. And their luminescence can be turned on and off really abruptly, as if by pushing a button."

This behaviour is known as intrinsic optical bistability. 

The low-power switching capabilities of the nanocrystals align with the global effort to reduce the amount of energy consumed by power-hungry applications like artificial intelligence, data centres and electronic devices. The power demands of AI have caused giants like Google to look at alternative power sources - in Google’s case, nuclear - to continue powering growing demand for AI.

AI applications not only demand substantial computational power, but they can often be constrained by limitations associated with existing hardware, a situation this research has the potential to address.

"Integrating photonic materials with intrinsic optical bistability could mean faster and more efficient data processors, enhancing machine learning algorithms and data analysis," Skripka said. "It could also mean more-efficient light-based devices of the type used in fields like telecommunications, medical imaging, environmental sensing, and interconnects for optical and quantum computers."

Additionally, Skripka added, the study complements existing efforts to develop powerful, general-purpose optical computers, which are based on the behaviour of light and matter at the nanoscale, and underscores the importance of fundamental research in driving innovation and economic growth.

"Our findings are an exciting development, but more research is necessary to address challenges such as scalability and integration with existing technologies before our discovery finds a home in practical applications," Skripka concluded.

The research was supported by the U.S. Department of Energy, the National Science Foundation and the Defense Advanced Research Projects Agency, which was led by Bruce Cohen and Emory Chan of Lawrence Berkeley, P. James Schuck of Columbia University and Daniel Jaque of the Autonomous University of Madrid.