BUFFALO, N.Y. — The tiny atomic defects so important for future quantum technologies can be difficult to spot. Fortunately, they leave behind some clues.
The defects can alter how a material responds to light, producing a distinctive optical fingerprint that scientists can measure.
The challenge is figuring out which fingerprints belong to which defects.
To that end, a University at Buffalo-led team has predicted the optical fingerprints of known atomic defects in hexagonal boron nitride (h-BN), a material with a honeycomb-like pattern of boron and nitrogen atoms. The team's computer models simulated how different defects affect the intensity and polarization of the light produced when h-BN is hit with a laser.
Published Oct. 19 in the American Chemical Society's Nano Letters , these calculations could eventually help scientists distinguish between different types of defects in h-BN and determine which could be useful for emerging quantum technologies.
"Not all atomic defects are created equal. Making it easier to identify defects brings us another step closer to determining which ones have the properties we're looking for," says co-corresponding author Vasili Perebeinos, PhD, professor in the Department of Electrical and Computer Engineering in the UB School of Engineering and Applied Sciences.
In total, the researchers modeled 10 different atomic defects, including those involving missing boron or nitrogen atoms and others in which carbon atoms had replaced them.
Some of these defects were predicted to dramatically increase the amount of light produced at double or even triple the frequency of the incoming laser, depending on the light's polarization, potentially making their optical fingerprints easier to measure.
Even defects containing the same atoms may produce different fingerprints, depending on how those atoms are arranged. The researchers modeled two different arrangements of four carbon atoms and predicted that one would produce a strong light signal in two different polarization directions, while the other would produce a strong signal in only one.
"These distinctive light responses could eventually allow us to experimentally identify not only which atoms are involved in a defect, but also precisely how they're arranged," says co-corresponding author Paras N. Prasad, SUNY Distinguished Professor, Samuel P. Capen Chair in the Department of Chemistry, and executive director of UB's Institute for Lasers, Photonics, and Biophotonics (ILPB).
Some of h-BN's defects can emit quantum light, including individual particles of light, known as photons, that are released one at a time. These single photons could carry quantum information for future communication and sensing technologies.
The researchers' work could eventually help scientists determine which defects produce quantum light and how to engineer defects for quantum technology applications.
"The ultimate goal is to create a material where we can precisely control the placement of defects that produce quantum light," Perebeinos says. "Instead of relying on individual sources of quantum light, we want to create entire arrays of them that could be used in future quantum technologies. That's the main motivation for studying defects in these materials."
The work was supported by the U.S. Air Force Office of Scientific Research as part of the Multidisciplinary University Research Initiative (MURI) . Support also came from the U.S. National Science Foundation, Australian Research Council, and the University at Buffalo Quantum Institute.
The study was led by PhD student Olga Savkina and postdoctoral associate Davoud Adinehloo, both in the Department of Electrical and Computer Engineering. Other co-authors from the department include Huamin Li, PhD, associate professor, and PhD students Pranati R. Kuntla and Viktor Labuntsov. Co-authors from the ILPB include Alexander Baev, PhD, and Andrey Kuzmin, PhD, research associate professors, and Cecilia L. A. V. Campos, PhD, a postdoctoral researcher. Co-authors from the University of Technology Sydney in Australia include professor Igor Aharonovich, PhD, and PhD student Ivan Zhigulin.
