Reviewed by Lexie CornerJun 3 2025
A study published in Advanced Materials reports that scientists at ETH Zurich have developed an ultra-thin lens capable of converting infrared radiation into visible light by halving the wavelength of the incoming light.
Schematics of a classic lens compared to a metalens. Image Credit: Ü. Talts / ETH Zurich
A study published in Advanced Materials reports that scientists at ETH Zurich have developed an ultra-thin lens capable of converting infrared radiation into visible light by halving the wavelength of the incoming light.
Lenses are among the most commonly used optical components. For example, camera lenses focus light to produce clear images or videos. The shift from bulky cameras to compact smartphone cameras illustrates recent progress in optical design.
However, even advanced smartphone cameras require a stack of lenses, often making the lens assembly the thickest part of the device. This is due to a fundamental limitation of traditional lens design: thick lenses are needed to bend light effectively and form a sharp image on the sensor.
In the past decade, researchers have worked to address this limitation, leading to the development of metalenses. These lenses are flat and mimic the behavior of conventional lenses. They are also significantly thinner—up to 40 times thinner than a human hair—and lighter, as they do not require glass.
Metalenses rely on a special metasurface made of structures only a few hundred nanometres in size. (One nanometre is one billionth of a metre.) These nanostructures can redirect light, allowing the lens to be much thinner and more compact.
When combined with certain materials, these nanostructures can also be used to study nonlinear optical phenomena. Nonlinear optics involves changing the color or wavelength of light. A common example is a green laser pointer, which starts with infrared light. This light passes through a high-quality crystal that converts it to green by halving its wavelength.
Lithium niobate is one material known for such properties. It is widely used in telecommunications to produce components that connect electronic systems with optical fibers.
Rachel Grange, a professor at ETH Zurich's Institute for Quantum Electronics, researches nanostructure fabrication using materials like lithium niobate. She and her team have developed a new method to produce metalenses from this material.
Their approach combines chemical synthesis with precise nanoengineering techniques.
The solution containing the precursors for lithium niobate crystals can be stamped while still in a liquid state. It works in a similar way to Gutenberg’s printing press.
Ülle-Linda Talts, Study Co-First Author and Doctoral Student, ETH Zurich
When heated to 600 °C, the material develops crystalline properties that enable it to convert light, similar to the process used in a green laser pointer.
The method offers several advantages. Producing lithium niobate nanostructures using conventional techniques is challenging due to the material’s high stability and rigidity. The researchers note that their approach is suitable for mass production because the inverse mold can be reused multiple times, allowing for repeated printing of metalenses as needed.
This method is also more cost-effective and faster to implement compared to existing techniques for fabricating miniaturized lithium niobate optical devices.
Ultra-Thin Lenses that Generate New Light
Researchers in Rachel Grange’s group at ETH Zurich used this method to produce the first lithium niobate metalenses with precisely engineered nanostructures. These devices function as standard light-focusing lenses but can also modify the wavelength of laser light. For example, when infrared light with a wavelength of 800 nanometers passes through the metalens, it generates visible light at 400 nanometers, which is directed to a specific point.
According to Grange, this light conversion is possible due to the unique structure and composition of the ultra-thin metalens, which enables a nonlinear optical effect. This phenomenon is not limited to a specific laser wavelength, making the technique adaptable for a range of potential applications.
From Counterfeit-Proof Banknotes to Next-Generation Microscopy Tools
Metalenses and similar hologram-generating nanostructures could serve as security features to help prevent counterfeiting of banknotes and securities, and to verify the authenticity of artworks. Their structural features are too small to be seen with visible light, but their nonlinear material properties allow for highly reliable verification.
Researchers can also use standard camera sensors to convert and guide laser light, making infrared light visible for sensing applications. This approach can also reduce the equipment needed for deep-ultraviolet (UV) light patterning in advanced electronics manufacturing.
These ultra-thin optical components, known as metasurfaces, represent a growing area of research at the intersection of chemistry, materials science, and physics.
We have only scratched the surface so far and are very excited to see how much of an impact this type of new, cost-effective technology will have in the future.
Rachel Grange, Professor, Institute for Quantum Electronics
Rachel Grange received a Swiss National Science Foundation (SNSF) Consolidator Grant, which supported this study.
Journal Reference:
Talts,-L. Ü., et al. (2025). Scalable Lithium Niobate Nanoimprinting for Nonlinear Metalenses. Advanced Materials. doi.org/10.1002/adma.202418957.