Illuminate previously unseen properties of materials
RPI Researchers Join Expertise at the Frontier of Light and Materials Research. Edwin Fohtung and Moussa N’Gom illuminate previously unseen properties of materials.
Researchers with the schools of science and engineering at Rensselaer Polytechnic Institute (RPI) are exploring new ways to manipulate matter with light to unlock a new generation of computer chips, photovoltaic cells and other advanced materials.
Physics professor Moussa N’Gom, Ph.D., and materials science professor Edwin Fohtung, Ph.D., have brought together their respective areas of expertise — optics and materials science — to illuminate previously unknown properties of the materials that will build the next generation of consumer, industrial and scientific devices.
“We can use almost the entire spectrum of light, from visible to x-ray, to manipulate and study materials,” Fohtung said. “We can interrogate any system, from hard condensed matter to soft biological tissue.”
Two of their findings, which explore how structured light can be used to alter and control material properties, were recently published in the journal Advanced Materials with the help of colleagues from RPI and Argonne National Laboratory.
In one of the papers, the researchers demonstrated that they can modulate the polarization of certain ferroelectric materials using light that has been “twisted,” or given a spiral waveform. They found that this gives them a great deal of control over the internal polarization of the material.
“We often think of light photons like a hammer, striking down on a material to switch its polarization on or off,” N’Gom said. “With this technique, however, we are using the photons more like a wrench: we can target a given set of atoms or ions in a crystal and manipulate the magnitude and configurations of the material’s internal electric field.”
They were able to capture detailed images of those manipulations using x-ray imaging. “The optical photons allow us to manipulate and form out-of-equilibrium configurations of the polarization textures, while the x-ray photons help us to capture three-dimensional images of the material’s internal structure,” Fohtung said.
It’s a proof-of-concept for new classes of non-volatile ferroelectric random-access memory (FeRAM) devices, similar in construction to the magnetic dynamic random-access memory (DRAM) devices used in conventional electronics. FeRAM devices could enable more information to be stored more efficiently in the same amount of space.
“Everybody wants their devices to be smaller, faster, store more information and be more secure,” Fohtung said. “We can do all those things with the method that we came up with. Using twisted light — light beams carrying orbital angular momentum (OAM) — to manipulate polarization textures represents a powerful, emerging strategy for designing FeRAM devices.”
In the second paper, taking a major step forward for clean energy and materials design, a research team led by N’gom and Fohtung captured, for the first time, real-time 3D images of structural atomic changes inside individual nanocrystals as they react to heat, gases, and light.
Using a cutting-edge technique called Bragg Coherent Diffractive Imaging (BCDI), the team observed how bismuth tungstate (Bi₂WO₆) nanoflakes — materials widely explored for photocatalysis and solar-driven chemical reactions — change their internal shape, stress, and structure under realistic operating conditions. “It’s like having X-ray vision into the heart of a single nanocrystal while it’s working,” Fohtung said.
This work overcomes a long-standing barrier in catalysis and energy materials: the inability to directly observe how single particles behave under real-world conditions. “These insights help us understand what drives performance — and failure — at the nanoscale,” Fohtung explained. “That means we can design smarter, more efficient materials from the ground up.”
In an experiment, the researchers found that exposure to intense light caused bismuth tungstate to break down, increasing the amount of surface area available to facilitate chemical interactions. They also found that the light could be used to induce a phase change in the catalyst from a metallic to a semiconducting state, effectively allowing them to switch the catalytic process on or off.
“Photocatalytic materials are significant for their unique capability to harness light energy to drive chemical reactions,” N’Gom said. “This collaborative work aims to show that structured light can be employed to enhance their activity under visible light and to control their physical properties such as recombination of charge carriers, thereby improving overall efficiency.”
“This work is a testament to the interdisciplinary nature of the research done at RPI, and to the creativity and inventiveness of our scholars,” said Gyorgy Korniss, Professor and Head of RPI’s Physics, Applied Physics and Astronomy department. “Advanced imaging techniques not only provide incredible tools to probe fundamental properties of materials and living cells, but also pave the way for the development of new computer chips, memory storage units, and other advanced devices and materials that will make all of our lives better in the coming decades.”
Source: Rensselaer Polytechnic Institute (RPI)
