Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory and the University of Chicago Pritzker School of Molecular Engineering (PME) have proposed a new type of memory, in which optical data is transferred from a rare earth element embedded within a solid material to a nearby quantum defect. Their analysis of how such a technology could work was published in Physical Review Research.

Above - Researchers at Argonne and the University of Chicago combined classical physics with quantum modeling to show how rare-earth elements (red dots) and defects (blue dots) within solids can interact to store optically encoded classical data. (Image by The University of Chicago.)

"We worked out the basic physics behind how the transfer of energy between defects could underlie an incredibly efficient optical storage method," said Giulia Galli, an Argonne senior scientist and Liew Family Professor at PME. "This research illustrates the importance of exploring first-principles and quantum mechanical theories to illuminate new, emerging technologies."

Most optical memory storage methods developed in the past, including CDs and DVDs, are limited by the diffraction limit of light. A single data point cannot be smaller than the wavelength of the laser writing and reading the data. In the new work, the researchers proposed boosting the bit density of optical storage by embedding many rare-earth emitters within the material. By using slightly different wavelengths of light -- an approach known as wavelength multiplexing -- they hypothesized that these emitters could hold more data within the same area.

To show the feasibility of the approach, Galli and her colleagues first studied the physics requirements necessary for efficient and dense optical storage. They created models of a theoretical material interspersed with atoms of narrow band rare-earth emitters. These atoms absorb light and re-emit that light at specific, narrow wavelengths. The researchers showed how this narrow wavelength light could then be captured by a nearby quantum defect.

Physical Review Research - First-principles investigation of near-field energy transfer between localized quantum emitters in solids

Researchers show a predictive and general approach to investigate near-field energy transfer processes between localized defects in semiconductors, which couples first-principles electronic structure calculations and a nonrelativistic quantum electrodynamics description of photons in the weak-coupling regime. The approach is general and can be readily applied to investigate broad classes of defects in solids. They apply the approach to investigate an exemplar point defect in an oxide, the F center in MgO, and they show that the energy transfer from a magnetic source, e.g., a rare-earth impurity, to the vacancy can lead to spin nonconserving long-lived excitations that are dominant processes in the near field, at distances relevant to the design of photonic devices and ultrahigh dense memories. They also define a descriptor for coherent energy transfer to predict geometrical configurations of emitters to enable long-lived excitations, that are useful to design optical memories in semiconductor and insulators.