Although modern cameras, microscopes, and other optical equipment have reached unprecedented levels of development in recent years, the optical technology used in all of these devices and instruments has not really changed much since its invention in the early 1700s. Even the most high-end equipment typically uses lensing technology developed around 1730.
The main function of lenses is to combine light waves of different lengths into a single beam, which would otherwise be focused at different points in the future image. The use of lenses solves the problem of chromatic aberration or violet halo that occurs in the event of defocusing, since light waves have different lengths. And although lenses are quite effective in this, the various materials used in their manufacture make them not always convenient and expensive. In addition, their production requires very careful and precise polishing and optical centering.
Scientists from the School of Engineering and Applied Sciences (SEAS) at Harvard University have developed a solution. They created a “metacorrector”. It is a single-layer surface of nanopillars (pictured above) spaced less than one wavelength apart, giving them the ability to manipulate the phases, amplitude and polarization levels of light, offering an easier, cheaper and more efficient way to correct chromatic aberration.
Image obtained with the meta-corrector (left) and without (right)
An additional plus of the technology is that it can be used in conjunction with conventional light-refracting optical components, which opens up wide possibilities for its application.
“Imagine that light splits into packets that travel at different speeds and reach the desired point at different times. Using nonopillars, the packets will reach the focal point at the same time, ”explains Wei Ting Chen, a researcher at the SEAS Applied Physics Laboratory and author of a published article describing the invention in the journal Nano Letters.
The developers of the metacorrector say the technology is “fundamentally different” from traditional correction methods because it uses nanostructured engineering.
“This allows us to go beyond the material limitations of lenses and achieve much higher performance,” adds co-author Alexander Zhu.
The technology can be applied to all kinds of commercial optical systems, from the simplest lenses to the most advanced microscopes, where up to 14 high-end lenses can be used, the scientists said.
The developers also add that they are going to further improve the efficiency of the meta-corrector so that the technology can be used in compact optical devices and other advanced technology.
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