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Scientists at the Institute of Quantum Electronics in Zurich, Switzerland, have created a tiny lens that converts infrared light into visible light.
It is noted that the lens reduces the wavelength of incoming infrared light by almost half, focusing it into a point. A team of scientists led by Professor Rachel Grange and doctoral students Ulle-Linda Thalts has created a flat metamaterial with a surface covered with nanostructures. These nanostructures are called metallins — ultra-thin sheets that can change the wavelength of light.
In their research, the scientists took advantage of a property called the generation of the second optical harmonic, during which photons with the same frequency, interacting with a nonlinear material, combine to form new photons with twice the energy, and thus with twice the frequency and a wavelength half that of the original. This was achieved by using lithium niobate, which exhibits nonlinear optical effects. However, its production on a nanoscale was extremely difficult.
Since lithium niobate is chemically and physically very stable, scientists decided to obtain its corresponding nanoscale structures by sto printed version using a sol-gel solution In liquid form, the material can be molded into nanostructures using soft nanoimprint lithography. After forming and firing at 600 °C, lithium niobate crystallizes into the type of nonlinear optical material used in telecommunications devices.
«The solution containing the precursors for lithium niobate crystals can be stamped while it is still in a liquid state It works in a similar way to the Gutenberg printing press»,” explains Ulle-Linda Thalts
On the basis of this, a metal plate with a thickness of less than a micron, which focuses the incoming infrared light, converting it into visible violet light. The lens was tested using a near-infrared laser at 800 nanometers, the output is a dense focal point at 400 nanometers — a direct conversion visible to the naked eye.
The lens increased the intensity of the output light by more than 30 times at the point of focus, over a wide range of wavelengths. The researchers emphasize that devices using similar lenses can be used in documents and banknotes to create a structure that is invisible under normal light, but with unmistakable optical signatures when illuminated by lasers.
Tiny cameras that convert infrared light into visible light have broad prospects for use in autonomous vehicles, medical diagnostics, and semiconductor manufacturing, reducing the cost and complexity of deep UV lithography. The technology enables scientists to improve advanced optical quantum tools. In particular, it is also about generating entangled photons using a process called spontaneous parametric frequency reduction and improves quantum communication and computing.
The team is also studying how to make the nanocrystals larger and reduce porosity, which will improve their nonlinear characteristics. Future developments may include improved resonances or finely tuned nanostructure geometries to further improve efficiency.
The results of the study were published in the journal Advanced Materials
Source: ZMEScience