Sogang University team develops new strategy for designing high-performance optical materials

A joint research team at Sogang University has developed a new strategy for designing optical materials that enable efficient wavelength conversion by effectively arranging three different optically active components within a single crystal.

The university said Monday that the findings were published last month in the Journal of the American Chemical Society, an internationally renowned chemistry journal.

The research team was led by Ok Kang-min, a professor in the Department of Chemistry, and Jang Joon-ik, a professor in the Department of Physics.

Zeng Wei, a postdoctoral researcher in the Department of Chemistry, served as the study’s first author, while Ok and Jang were co-corresponding authors.

Nonlinear optical materials enable the conversion of laser light into light of different wavelengths. They are used in a wide range of applications, including high-performance lasers, precision optical measurements, optical communications and advanced photonic technologies.

However, achieving superior optical performance requires more than simply combining components that respond strongly to light. The way these components are oriented and arranged within a crystal, as well as how they interact with one another, is equally important.

To address this challenge, the research team focused on peroxomolybdates, a new class of crystalline materials composed of molybdenum, peroxide groups and organic molecules.

Using a strategy called coordination-site engineering, the team synthesized three new types of crystals by varying the number of coordination sites through which organic molecules bind to metal ions from one to three.

The researchers found that changing the way organic molecules bind altered the atomic arrangement and symmetry within the crystals, resulting in noncentrosymmetric structures in which different optically active components were effectively aligned.

The team confirmed that the pi-electron systems of organic molecules, molybdenum centers and the electronic structures of peroxide groups work together to contribute to nonlinear optical properties.

The university said the most notable achievement was the material’s wavelength conversion performance.

When exposed to a 1,300-nanometer laser, the newly developed crystal produced a second-harmonic generation signal 34.9 times stronger than that of potassium dihydrogen phosphate, a widely used nonlinear optical reference material.

The crystal also demonstrated excellent resistance to high-intensity laser irradiation, highlighting its potential as a next-generation material for laser wavelength conversion.

The study was made possible through close collaboration between chemistry and physics.

“The significance of this research lies not simply in discovering a material that produces a strong optical signal, but in introducing a new approach to designing crystals in which different optically active components work together,” Ok said.

He added, “This design principle could also be applied to the development of various high-performance optical crystals in the future.”

“This collaborative research is significant in that it has established a link between crystal structures and wavelength conversion performance through precise measurements and analysis of the new material’s optical properties,” said Jang.

“It demonstrates how interdisciplinary research combining chemistry and physics can open up new possibilities for developing next-generation optical materials,” he added.