UC Irvine Engineering Researchers Develop New Method for Controlling Light in Nanomaterials

Findings open a simpler path to tunable nanoscale optical materials

May 28, 2026 - A team of researchers led by Assistant Professor Maxim Shcherbakov in the UC Irvine Nhu Department of Electrical Engineering and Computer Science has developed a simple way to change how infrared light moves through an ultrathin crystal – using only heat and pressure.

The study, published in ACS Nano, was carried out in collaboration with researchers from UCI’s Department of Physics and Astronomy and Department of Mechanical and Aerospace Engineering. It shows that carefully introduced defects inside a crystal can provide a new way to tune its optical behavior without complex fabrication or chemical additives.

The findings point to a new strategy for controlling light in nanomaterials: rather than adding complexity, researchers can make carefully chosen changes within the material itself. The material at the center of the work is alpha-molybdenum trioxide, or α-MoO₃, a layered crystal known for its unusual interaction with infrared light. In this material, light couples with the crystal lattice vibrations, forming hybrid waves called phonon polaritons. These waves can confine infrared energy to spaces far smaller than the wavelength of light itself, making them promising for future technologies, such as compact sensors, thermal imaging systems and nanoscale optical circuits.

A major challenge, however, has been finding practical ways to control these waves. Previous methods often relied on intricate nanofabrication, chemical modification or energetic particle beams, which can damage the material or reduce its performance.

The UCI team found a gentler alternative. They placed thin α-MoO₃ flakes between silicon wafers, applied mild pressure, and heated them to temperatures comparable to those of a household oven. This treatment removed a small number of oxygen atoms from the crystal, leaving behind atomic-scale vacancies. The heating and cooling process also left the material slightly compressed.

“What is exciting about this approach is its simplicity,” said Mashnoon Alam Sakib, a graduate student in Shcherbakov’s group and the study’s first author. “Instead of building complicated nanostructures or introducing foreign elements, we use a straightforward thermal process to reshape the material’s optical behavior from within.”

To observe the effect, the researchers used photo-induced force microscopy, a technique capable of mapping nanoscale light waves that are invisible to ordinary microscopes. They found that the treated crystals carried polariton waves with noticeably altered wavelengths—an average shift of about 13%, reaching up to 24% in some regions.

“These waves are far too small to observe with conventional optics,” said Naveed Hussain, a former postdoctoral researcher in Shcherbakov’s group, now at Toyota Research Institute of North America. “The microscopy allowed us to directly visualize how the heat-and-pressure treatment changed the way infrared energy travels through the crystal.”

Importantly, the material retained much of its performance. Modifying a crystal often causes light-based waves to fade more quickly, but in this case, the engineered polaritons remained relatively long-lived, with only a moderate reduction compared with the untreated material.

“There is usually a trade-off between tuning a material and preserving the quality of the waves it supports,” Shcherbakov said. “Here, we were able to achieve a meaningful change in optical response while keeping the polaritons robust enough to remain useful.”

UCI researchers collaborating on the study include Mariia Stepanova and Kumar Wickramasinghe from the Nhu Department of Electrical Engineering and Computer Science; William Harris, Joshua Bocanegra and Ruqian Wu from the Department of Physics and Astronomy; and Juan Diego Sanchez and Camilo Velez from the Department of Mechanical and Aerospace Engineering.