Coding of Non‐Linear White‐Light Luminescence from Gold‐Silicon Structures for Physically Unclonable Security Labels

Luminescent security labels are effective platforms for protection of consumer goods from counterfeiting. However, the lifetimes of such security approaches are limited due to narrow-band photoluminescent features of the label elements, which can be used for the protection technology disclosure. In this paper, a novel concept for the application of non-linear white-light luminescence from hybrid metal-semiconductor structures fabricated by direct femtosecond laser writing for the creation of physically unclonable security labels is proposed. A close connection is demonstrated between the internal composition of hybrid structures, which is controlled at the fabrication stage, and their non-linear optical signals. It is shown that the application of decorrelation procedure based on discrete cosine transform and polar codes for label coding can overcome the problem of the white-light photoluminescent spectra correlation. The proposed fabrication approach and coding strategy allows reaching a high degree of device uniqueness (up to 99%), bit uniformity (close to 0.5), and encoding capacity up to 1.25 x 10(437) in a single label element. The results demonstrate that the barriers for the application of white-light luminescent nano-objects for the creation of physically unclonable labels are removed.