الوضع الليلي
11:53:45 
2025-07-20 
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Imagine a chip so thin it looks like nothing—until you shine twisted light on it. Scientists have developed a metasurface that can hide and reveal two entirely different images depending on the light’s polarization.
Using carefully arranged nano-structures, this technology doesn’t just trick the eye—it opens doors to next-gen encryption, biosensing, and quantum tech. From invisible watermarks to detecting drug purity, this flat device uses the fundamental physics of “handedness” to unlock secrets nature and science have long kept hidden.
Twisted Light and Chiral Interactions
Trying to put a left-handed glove on your right hand doesn’t work because the two are mirror images—they look similar but don’t align. This concept, known as “chirality,” is a key principle in biology, chemistry, and materials science. In nature, most DNA strands and sugars are right-handed, while most amino acids are left-handed. If a molecule’s handedness is flipped, it can stop functioning correctly. A nutrient may become ineffective, or a medication might lose its benefits or even become dangerous.
Light, too, can have a kind of handedness. When light is circularly polarized, its electric field rotates as it moves forward, forming either a left-handed or right-handed spiral. Chiral materials respond differently to each type of polarized light. By shining circularly polarized light on a substance and measuring how each spiral is absorbed, reflected, or delayed, scientists can learn about the material’s own chirality. But because these interactions are extremely subtle, controlling chirality with precision has been a long-standing challenge.
Metasurfaces: The New Chiral Engineers
Now, scientists from the Bionanophotonic Systems Laboratory in EPFL’s School of Engineering have collaborated with those in Australia to create artificial optical structures called metasurfaces: 2D lattices composed of tiny elements (meta-atoms) that can easily tune their chiral properties. By varying the orientation of meta-atoms within a lattice, scientists can control the resulting metasurface’s interaction with polarized light.
“Our ‘chiral design toolkit’ is elegantly simple, and yet more powerful than previous approaches, which tried to control light through very complex meta-atom geometries. Instead, we leverage the interplay between the shape of the meta-atom and the symmetry of the metasurface lattice,” explains Bionanophotonics Lab head Hatice Altug.
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