Researchers from the School of Materials Science and Engineering at Shanghai Jiao Tong University are demonstrating a new approach to data security by directly writing encrypted information onto metasurfaces using femtosecond lasers. This technique bypasses the need for high-precision nanofabrication, a significant limitation of current metasurface-based encryption methods. The system uniquely layers visible light and infrared information without interference, creating a dual-layer encryption scheme where a QR code in infrared becomes clearly displayed at 300°C. This combination of advanced encryption with everyday accessibility addresses a critical need for more robust and versatile security measures in an increasingly complex digital world, as information security has become the foundation for safeguarding data.
Femtosecond Laser Maskless Direct Writing for Metasurface Fabrication
This advancement addresses a critical limitation in metasurface technology; previously, practical application was hampered by reliance on intricate optical decryption systems and high-precision lithography. The team can write visible/infrared dual-band information on pure zirconium refractory metal substrates, achieving crosstalk-free hierarchical regulation of visible light information and infrared information. This dual-layer encryption is noteworthy, as it allows for different decryption methods depending on the wavelength of light used. Infrared data, for example, is embedded as a QR code readable by a standard mobile phone scanner; at 300°C, the code is clearly displayed, revealing content from Shanghai Jiao Tong University’s homepage. Visible light information, conversely, can be erased with heat, offering a unique security feature. The “SJTU” and “Shanghai” patterns disappear at 300℃, demonstrating the ability to verify if information has been maliciously read or rewritten.
This process leverages the unique properties of zirconium, a refractory metal, to increase decryption temperatures and enhance the durability of the encrypted data. Researchers found that “LIPSS structuring along with the reducing ability and low oxygen defect oxidation ability in the ethylene glycol liquid phase environment are the main reasons for the differential color development,” explaining the mechanism behind the dual-band information writing. The work, published in Opto-Electronic Advances, represents a significant step toward all-in-one, high-security encryption metasurfaces.
Dual-Band Visible/Infrared Information Encoding on Zirconium
Current methods of optical encryption often demand intricate decryption setups and rely heavily on precise nanofabrication, particularly electron beam lithography, limiting widespread adoption. Researchers are increasingly turning to metasurfaces for enhanced security, sometimes combining them with stimuli like light or heat, but these approaches still face challenges in practical application. A team from the School of Materials Science and Engineering, Shanghai Jiao Tong University has proposed a new approach utilizing femtosecond laser maskless direct writing (fs-LMDW) to address these limitations. This team can write visible/infrared dual-band information on pure zirconium refractory metal substrates, achieving crosstalk-free layering. The process begins by engraving infrared information, such as a QR code linking to the Shanghai Jiao Tong University official website, using a femtosecond laser in an air environment; this creates structures exhibiting rich oxygen vacancies and appearing uniformly black.
Subsequently, the substrate is immersed in an ethylene glycol environment, where gray visible light information, patterns including “SJTU”, “Shanghai”, and “Jiaotong” is written with the same laser, carefully avoiding disruption of the underlying infrared data. This “temperature-controlled key” leverages zirconium’s refractory properties, significantly increasing decryption temperature compared to phase change materials.
cannot be completely erased at 300°C, demonstrating the one-time complete erasure capability of the sample, which can effectively verify whether the information has been maliciously read and rewritten.
High-Temperature Erasability & Rewritability Demonstrate Security
This method addresses a critical limitation in optical encryption, the reliance on intricate manufacturing techniques, by leveraging the capabilities of fs-LMDW technology, which offers fast operation, scalability, and material versatility, particularly with difficult-to-process refractory metals. The researchers discovered that LIPSS structuring, combined with the properties of an ethylene glycol liquid environment, is key to the differential color development used for visible light writing, and oxidation at high temperatures is responsible for its erasability. This work published in Opto-Electronic Advances builds on years of research into femtosecond laser processing and material interface modification, with the goal of creating multi-functional metasurfaces for information encryption and infrared camouflage.
simple and fast operation, no environmental dependence, strong cross-scale processing capability, which can realize customized patterning processing from micron to nanometer scale, excellent structural reconfigurability, material universality, especially obvious advantages in micro-nano processing of difficult-to-process materials such as refractory metals, and wide compatibility with other processing techniques.
LIPSS Structuring & Oxidation Mechanisms in Information Control
The development of secure data storage increasingly relies on physical methods, moving beyond purely digital solutions, and researchers are now detailing how precisely controlled oxidation plays a critical role in a novel encryption technique. This builds on the growing field of metasurface technology, which offers potential for multi-channel, high-security encryption, but circumvents the typical need for complex optical decryption systems and high-precision nanofabrication. Central to this approach is understanding how femtosecond laser processing interacts with the zirconium substrate at a microscopic level. This dual-layer system offers unique security features; visible light information is not only readable but also erasable with heat, as demonstrated by the disappearance of the “SJTU”, “Shanghai”, and “Jiaotong” patterns at 300℃, demonstrating the ability to verify whether the information has been maliciously read and rewritten.
information security has become the “lifeline” for safeguarding personal privacy, corporate secrets, and national information.
