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Researchers In Zurich Create Lens With Nanostructures That Converts Infrared Into Violet And Could Revolutionize Cameras, Security And Semiconductors
In a laboratory in the city of Zurich, Switzerland, scientists achieved an impressive feat. They managed to construct a lens capable of converting invisible infrared light into visible light.
The lens, slightly thicker than a red blood cell, transforms the infrared beam that passes through it into visible violet light and focuses it with extreme precision.
The advancement was recently published in the journal Advanced Materials. The work represents a new path for lens construction, using tiny structures resembling teeth, molded in a special crystal, through a technique inspired by the printing process.
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This new type of lens has the potential to revolutionize various areas. From the manufacturing of smartphone cameras to the development of anti-counterfeiting technologies, the applications are vast and promising.
Flat Lenses With Extraordinary Properties
For centuries, the design of lenses has maintained practically the same principle: curved pieces of glass redirecting light to a focal point.
The team from ETH Zurich, led by Professor Rachel Grange and PhD candidate Ülle-Linda Talts, took a different path. They developed a flat metamaterial, that is, an artificial material with properties that do not exist in nature.
The surface of this metamaterial was patterned with nanostructures called metalenses. These ultrathin sheets manipulate light with high precision, acting on scales smaller than the wavelength of light.
The group went beyond mere redirection of light. They altered the color of the light beam using a phenomenon called “second harmonic generation.”
In this process, two low-energy photons combine to form a single photon with higher energy. It’s like taking two long red threads and twisting them to form a short, bright violet thread.
The Essential Role Of Lithium Niobate
To achieve this feat, it was necessary to use a very specific material: lithium niobate. This compound is already widely used in optical telecommunications due to its ability to manipulate light through nonlinear effects.
However, working with it at the nanoscale has always been a challenge due to its chemical and physical resistance.
The team then developed a new approach. They created a liquid version of lithium niobate, based on a sol-gel solution.
In this state, the material can be shaped into nanostructures using soft nanoimprinting lithography, a technique similar to printing text on paper. After the mold is completed, the material is heated to 600 °C and crystallizes, retaining its nonlinear optical properties.
“This solution containing the precursors of lithium niobate crystals can be stamped while still in a liquid state,” explained researcher Talts. “It works similarly to a Gutenberg press.”
Precise And Intense Results
The result was the creation of a metalens with a thickness of less than one micron. This lens was able to not only focus the incident infrared light but also convert it into visible violet light. In tests, the team used an infrared laser with a wavelength close to 800 nanometers. The lens converted the light into a 400-nanometer beam, making the result visible to the naked eye.
The lens’s performance was impressive. It increased the intensity of the emitted light by more than 30 times at the focal point. Additionally, it operated efficiently over a wide range of wavelengths, from near-infrared to near-ultraviolet, without relying on fragile resonance effects.
Another notable point was the use of polycrystalline lithium niobate, composed of small randomly oriented domains. Each of the nanostructures, called “meta-atoms,” acted like small antennas, directing and converting light based on carefully planned geometry.
Possible Applications In The Future
For now, this advancement remains restricted to the research environment. However, the potential applications are broad and could impact various industries.
In the security sector, for example, these metalenses could be used in documents and currency. As their structures are not visible under normal light, it would be possible to create unique optical signatures, visible only under laser, making counterfeiting more difficult.
In the area of imaging and sensors, the technology could allow compact cameras to detect infrared light. This feature is essential for night vision equipment, autonomous vehicles, and also for medical examinations, all without the need for large, costly optical devices.
In the semiconductor industry, the new lens could help reduce the costs and difficulties of deep ultraviolet lithography, a process used in manufacturing modern microchips.
In the field of fundamental science, the advancement opens doors for new research in quantum optics. The technique can be applied in generating entangled photons through spontaneous parametric down-conversion, an important process for quantum communications and computing.
Advancements And Challenges For The Future
Despite the promising results, the technology is still recent and can be improved. Although the current resolution of the lens is already impressive, there is room for improvements in performance.
Among the next steps, the team aims to incorporate advanced resonances and refine the geometries of the nanostructures to further increase efficiency.
Additionally, scientists are exploring ways to create larger nanocrystals and reduce the porosity of the material. These improvements would enhance the nonlinear performance of the lens.
“So far, we have only scratched the surface,” said Professor Rachel Grange.
Even so, the research represents an important milestone in the field of optics. It shows that it is possible to transform and control light with ultrathin printed materials.
In a world where devices are becoming smaller and more sophisticated, the way light is manipulated also needs to evolve. Now, with a lens thinner than a human hair, researchers at ETH Zurich demonstrate that even light can be completely reshaped.
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