Catenaa, Friday, March 13, 2026- Researchers in the Netherlands have identified a two-dimensional crystal capable of bending ultraviolet light more strongly than any material previously measured, a discovery that could advance chip manufacturing and photonic technologies.
Scientists from Delft University of Technology and Radboud University reported that the layered compound CuInP2S6 displays unusually strong birefringence, a property that causes light to split into two rays traveling at different speeds inside a material.
The research appeared in the journal Advanced Optical Materials and describes how the crystal can change its refractive behavior dramatically depending on thickness, enabling precise control of ultraviolet light.
Lead researcher Houssam El Mrabet Haje said experiments showed the material can alter its refractive index by about 25 percent as its thickness changes from bulk crystals to layers only tens of nanometers thick.
Near ultraviolet wavelengths around 340 nanometers, the difference between the crystal’s two refractive directions reached 1.24, far higher than conventional birefringent materials. By comparison, the mineral calcite typically exhibits birefringence of about 0.17, while rutile reaches around 0.30.
Scientists say the extreme effect arises from the crystal’s ferroelectric structure. In CuInP2S6, copper ions can shift within atomic layers, creating electric polarization that interacts with incoming light. When the crystal is thinned to nanometer scales, the movement of those ions becomes constrained, producing strong changes in optical response.
The team found that the material’s in-plane refractive index can reach about 2.85 in the ultraviolet range, while the perpendicular direction measures near 1.61. The resulting contrast produces the unusually large birefringence without requiring complex nanostructuring.
Researchers say the effect could enable compact devices that manipulate ultraviolet and blue light on semiconductor chips.
Ultraviolet optics are widely used in advanced manufacturing, particularly in systems built by companies such as ASML that produce extreme ultraviolet lithography tools used to fabricate leading-edge microchips.
Those systems require precise control of polarization and light propagation. Conventional optical components that perform those tasks often rely on large crystalline wave plates or complex nanostructured surfaces.
Because CuInP2S6 can be exfoliated into extremely thin layers similar to other two-dimensional materials, scientists believe it may be integrated directly onto photonic circuits.
The crystal also belongs to a class of materials known as van der Waals ferroelectrics, whose layers are held together by weak forces that allow them to be peeled into thin sheets. That structure enables researchers to transfer the material onto silicon photonic devices with minimal processing.
Laboratory measurements suggest that optical losses remain relatively low even at ultraviolet wavelengths, while the material can tolerate temperatures ranging roughly from minus 50 to 150 degrees Celsius.
Researchers say the properties could allow engineers to create chip-scale devices such as polarization rotators, optical modulators and miniature isolators that control signal direction in optical circuits.
Such components are essential for fiber-optic communications networks and emerging integrated photonics technologies used in data centers and quantum communication systems.
The discovery also suggests that other layered ferroelectric crystals containing mobile ions may exhibit similar optical behavior.
Scientists plan additional studies to test device prototypes and examine how the optical response changes under electric fields, mechanical strain and different wavelengths of light.
If the material proves scalable for manufacturing, researchers say it could form the basis of new ultraviolet photonic components capable of operating directly on semiconductor chips.
