(Nanowerk Spotlight) Light carries information in its wavelength, wavevector direction, polarization, and the way it bends through materials. Until now, optical data storage has typically used just one of these properties at a time—like encoding data in different colors of light. This limitation makes optical storage vulnerable to unauthorized access and restricts how much information can be packed into a given space.
A research team at Wuhan University has created a metasurface—an engineered surface with precisely arranged nanoscale structures—that can manipulate all these properties of light simultaneously. Their innovation, reported in Advanced Materials (“Multidimensional-Encrypted Meta-Optics Storage Empowered by Diffraction-Order Decoupling”), allows a single physical device to encode information in sixteen different ways, making the data both more secure and more densely packed than conventional optical storage methods.
The key advance lies in controlling how light bends, or diffracts, when it hits the metasurface. Previous designs forced different orders of diffracted light to follow fixed patterns, like light splitting through a prism. The new approach breaks these constraints, allowing each order of diffracted light to be controlled independently using a detour phase encoding method that avoids complex multi-cell structures.
These metasurfaces, composed of silicon structures shaped like tiny pillars and arranged on a silicon nitride base, can process both blue and green light coming from multiple directions. Each pillar’s exact position and orientation determines how it manipulates incoming light. The collective behavior of these pillars creates a sophisticated optical device that responds differently to various combinations of light properties.
Think of it as a lock with four separate keys that must all match perfectly to access the information. The metasurface only reveals specific holographic images when illuminated with exactly the right color of light, from the correct angle, with the proper polarization, hitting the surface in precisely the right way. Any mismatch and the stored information remains inaccessible. Because multiple optical dimensions are modulated simultaneously, brute-force decryption becomes exponentially more difficult, significantly enhancing security.
Schematic of multidimensional encrypted meta-optics storage based on order-decoupled metasurface. a) Concept of order-decoupled metasurface and comparison with conventional metasurface. Conventional metasurfaces can only uniformly manipulate the light field in each order, while order-decoupled metasurfaces are able to independently encode phase profiles in multiple orders. b) Schematic diagram of multidimensional encrypted holography. The diagram showcases the capability of the meta-optics for manipulating light in four degrees of freedom: (i) Polarization, (ii) Wavevector Direction, (iii) Diffraction Order, and (iv) Wavelength, which enables then the independent encoding of up to sixteen holograms. (Image: Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)
The researchers demonstrated this capability by encoding different letters that only become visible under specific combinations of light properties. When viewed with blue light at 480 nanometers wavelength from one angle, the device might display one image, while green light at 532 nanometers from another angle reveals something completely different. This holographic approach not only enhances storage security but also has potential applications in augmented reality (AR) display technologies, where digital images must be precisely overlaid onto real-world backgrounds.
The fabrication process uses established semiconductor manufacturing techniques, making it potentially compatible with existing production facilities. The team developed sophisticated computer algorithms to determine the exact arrangement and shape of nanopillars needed to achieve the desired optical effects. To minimize interference between different holographic channels, they employed an optimization strategy based on simulated annealing, which helped refine phase retrieval and reduce crosstalk between encoded images.
In testing, about 3.1% of the input light energy successfully created the intended holographic images. While this efficiency leaves room for improvement, it proved sufficient to demonstrate the technology’s potential for secure data storage and display applications.
The implications extend beyond data security. The ability to control multiple light properties independently makes this technology promising for augmented reality displays, where digital information needs to be precisely overlaid onto the real world. It could also enable new anti-counterfeiting measures and advance optical computing capabilities.
This metasurface technology represents a fundamental shift in how light can be manipulated to store and protect information. By requiring multiple precise conditions to access stored data, it creates a robust security barrier while maintaining legitimate access. The work demonstrates how controlling multiple properties of light simultaneously enables new capabilities in optical engineering and information security.
The Wuhan University team’s achievement opens new possibilities in optical technology, offering innovative solutions for secure data storage while advancing the fields of holographic displays, AR applications, and optical computing. Their approach to manipulating multiple properties of light simultaneously provides a blueprint for developing more sophisticated optical devices.
Get our Nanotechnology Spotlight updates to your inbox!
Thank you!
You have successfully joined our subscriber list.
Become a Spotlight guest author! Join our large and growing group of guest contributors. Have you just published a scientific paper or have other exciting developments to share with the nanotechnology community? Here is how to publish on nanowerk.com.
