Femtosecond laser method enables dual-band encryption metasurface on zirconium

By AI, Created 10:27 AM UTC, May 20, 2026, /AGP/ – Researchers at Shanghai Jiao Tong University say they have built a high-security encryption metasurface that can write visible and infrared information on the same zirconium substrate without crosstalk. The approach could reduce dependence on complex decryption systems and high-precision lithography while adding a temperature-controlled key for decoding.

Why it matters: - The work points to a simpler manufacturing path for optical encryption metasurfaces, which are being explored for privacy protection, authentication, anti-counterfeiting and secure data storage. - The team says the zirconium platform combines dual-band information storage with high-temperature control, raising the bar for selective decryption. - The method could reduce reliance on electron-beam lithography and other high-precision nanofabrication tools.

What happened: - Researchers from the School of Materials Science and Engineering at Shanghai Jiao Tong University published the study in Opto-Electronic Advances. - The paper is titled “Femtosecond Laser Maskless Direct Writing of Dual-Band Crosstalk-Free Information for All-In-One High-Security Encryption Metasurface.” - The reported system uses femtosecond laser maskless direct writing on pure zirconium refractory metal substrates. - The publication DOI is 10.29026/oea.2026.250303.

The details: - The team wrote infrared information first in air using gradient micro-nano structures, including a QR code linked to Shanghai Jiao Tong University. - The infrared pattern appears black because oxygen vacancies help hide the information. - The substrate was then placed in ethylene glycol, where the laser wrote gray visible-light information such as “SJTU,” “Shanghai” and “Jiaotong”. - The visible-light pattern was limited to the nanometer scale, so it did not damage the micro-scale infrared structure. - The result was crosstalk-free dual-band writing, with spatial structure and optical response regulated together. - The visible-light information is erasable at high temperature and can be rewritten by laser. - The SJTU and “Shanghai” patterns disappeared at 300°C. - A rewritten “Jiaotong” pattern was still visible after laser rewriting and could not be completely erased at 300°C. - The infrared QR code became visible in stages as temperature increased. - At 300°C, the QR code was fully readable by phone scan and linked to Shanghai Jiao Tong University’s homepage. - The sample demonstrates a temperature-controlled key for decryption and verification against malicious readout or rewriting. - Comparative characterization linked the visible-color effect to laser-induced periodic surface structures and reactions in the ethylene glycol environment. - High-temperature oxidation was identified as the mechanism behind the erasure of the visible-light information.

Between the lines: - The study is trying to solve two bottlenecks in metasurface encryption at once: how to write multiple information channels on one surface and how to do it without expensive lithography. - Refractory metals like zirconium give the system more thermal stability than phase-change-material approaches, which can lower the decryption temperature. - The use of temperature as a key adds a physical layer of security that is harder to imitate than software-only protection.

What’s next: - The researchers say the approach could support future work in information encryption and infrared camouflage. - Wider adoption will likely depend on whether the writing process can be scaled while preserving the same dual-band, crosstalk-free performance.

The bottom line: - Shanghai Jiao Tong University researchers have turned femtosecond laser processing of zirconium into a dual-channel encryption surface that can store, hide, erase and rewrite information with temperature-based access control.