At a Glance
- Researchers at ETH Zurich have developed an innovative, ultra-thin metalens that can simultaneously focus light to a single point and transform its color from infrared to visible.
- The novel device is the first metalens to be fabricated from lithium niobate (LiNbO3), a material prized for its optical qualities but notoriously difficult to shape at the nanoscale.
- Scientists pioneered a cost-effective “printing press” technique that stamps liquid precursors into a precise mold, overcoming the challenges of working with the extremely hard crystalline material.
- The lens successfully converted invisible 800-nanometer light into focused 400-nanometer violet light, increasing the intensity of the new color by as much as 34 times.
- This breakthrough enables scalable production for applications like advanced anti-counterfeiting security features, next-generation microscopy tools, and other powerful, miniaturized optical technologies for various industries.
Physicists at ETH Zurich have pioneered a novel fabrication technique to create an ultra-thin lens that can focus light and change its color. These innovative components, known as metalenses, replace the bulky, curved glass in traditional optics with a flat surface engineered with structures just nanometers in size. While typical metalenses only bend light, this new device, the first of its kind made from the material lithium niobate (LiNbO3), can convert invisible infrared light into visible violet light. The breakthrough, detailed in Advanced Materials, paves the way for more compact and versatile optical systems.
The lens’s unique ability stems from nonlinear optics, where a material interacts with intense light, such as from a laser, to generate new light at different frequencies or colors. This is the same principle used in green laser pointers, which use a special crystal to double the frequency of infrared light, turning it into green light. The researchers used lithium niobate, a material prized for its excellent nonlinear properties. However, lithium niobate is extremely hard and chemically inert, making it notoriously difficult to sculpt into the precise, nanoscale patterns required for a metalens. To overcome this, the team developed a “bottom-up” method based on nanoimprint lithography, a process they liken to Gutenberg’s printing press. A liquid solution containing the chemical precursors for lithium niobate is stamped with a nanoscale mold and then heated to 600 degrees Celsius, forming a solid, crystalline structure with the desired optical properties.
In demonstrating their new technology, the researchers built a metalens capable of performing a second-harmonic generation process. When they directed an infrared laser with a wavelength of 800 nanometers through the device, the lens not only focused the beam to a sharp point but also halved its wavelength, transforming it into 400-nanometer violet light. This conversion was remarkably efficient, with the precisely engineered nanostructures boosting the intensity of the new violet light by up to 34 times compared to a simple, unstructured film of the same material. This successful demonstration marks a significant advance for nonlinear metasurfaces, which are optical components designed to manipulate light in complex ways.
This new fabrication method’s cost-effective and scalable nature opens the door to a wide range of applications. These nonlinear metalenses could be used as advanced security features on banknotes or official documents, creating invisible patterns to the naked eye. However, they can be authenticated with a specific type of light. In scientific research, they could simplify complex imaging systems by allowing standard cameras to detect infrared signals or streamlining the fabrication of next-generation electronics. As a relatively new field at the intersection of physics and materials science, developing such metasurfaces is just beginning, promising a future of powerful, miniaturized optical technologies.
References
- Rüegg, P. & E. T. H. Zurich. (2025, June 2). Ultra-thin lenses halve incident wavelength to make infrared light visible. Phys.Org; E. T. H. Zurich. https://phys.org/news/2025-06-ultra-thin-lenses-halve-incident.html
- Talts, Ü., Weigand, H., Occhiodori, I., & Grange, R. (2025). Scalable lithium niobate nanoimprinting for nonlinear metalenses. Advanced Materials, 2418957. https://doi.org/10.1002/adma.202418957
