Researchers unlock light-matter interactions at sub-nanometer scales, leading to ‘picophotonics’

Purdue University researchers have discovered new waves with picometer-scale spatial variations of electromagnetic fields that can propagate in semiconductors like silicon. The research team, led by Dr. Zubin Jacob, Elmore Associate Professor of Electrical and Computer Engineering and the Department of Physics and Astronomy, published their findings in Applied physical examination in an article entitled “Picophotonics: anomalous atomic waves in silicon”.

“The word microscopic has its origins in the length scale of a micron, which is a million times smaller than a meter. Our work concerns the light-matter interaction in the picoscopic regime which is much smaller, where the discrete arrangement of atomic lattices changes the light’s properties in surprising ways,” says Jacob.

These intriguing findings demonstrate that natural environments harbor a variety of rich light-matter interaction phenomena at the atomistic level. The use of picophotonic waves in semiconductor materials can lead researchers to design new functional optical devices, allowing applications in quantum technologies.

The light-matter interaction in materials is at the heart of several photonic devices, from lasers to detectors. Over the past decade, nanophotonics, the study of how light travels at the nanoscale through man-made structures such as photonic crystals and metamaterials, has led to significant advances. This existing research can be captured in the realm of classical theory of atomic matter. The current discovery leading to picophotonics was made possible by a major leap forward using a quantum theory of atomistic response in matter. The team is made up of Jacob as well as Dr. Sathwik Bharadwaj, a researcher at Purdue University, and Dr. Todd Van Mechelen, a former post-doctoral fellow at Purdue University.

The longstanding enigma in the field has been the missing link between atomic lattices, their symmetries, and the role it plays on deeply picoscopic light fields. To answer this conundrum, the theory team developed a Hamiltonian Maxwell framework of matter combined with a quantum theory of light-induced response in materials.

“This is a radical departure from the classical processing of light flux applied in nanophotonics,” says Jacob. “The quantum nature of the behavior of light in materials is key to the emergence of picophotonic phenomena.”

Bharadwaj and his colleagues showed that hidden among the well-known traditional electromagnetic waves, new anomalous waves emerge in the atomic network. These light waves are highly oscillatory even within a fundamental element of the silicon crystal (sub-nanometer length scale).

“Natural materials themselves have rich intrinsic crystal lattice symmetries and light is strongly influenced by these symmetries,” Bharadwaj explains. “The next immediate goal is to apply our theory to the plethora of quantum and topological materials and also to experimentally verify the existence of these new waves.”

“Our group is at the forefront of research on pico-scale electrodynamic fields inside matter at the atomistic level,” says Jacob. “We recently launched the Picoelectrodynamics Theory Network, where we bring together diverse researchers to explore macroscopic phenomena arising from microscopic picoelectrodynamic fields inside matter.”