Hybrid Plasmonic/Photonic Nanoscale Strategy for Multilevel Anticounterfeit Labels

Abstract

Innovative goods authentication strategies are of fundamental importance considering the increasing counterfeiting levels. Such a task has been effectively addressed with the so-called physical unclonable functions (PUFs), being physical properties of a system that characterize it univocally. PUFs are commonly implemented by exploiting naturally occurring nonidealities in clean-room fabrication processes. The broad availability of classic paradigm PUFs, however, makes them vulnerable. Here, we propose a hybrid plasmonic/photonic multilayered structure working as a three-level strong PUF. Our approach leverages on the combination of a functional nanostructured surface, a resonant response, and a unique chromatic signature all together in one single device. The structure consists of a resonant cavity, where the top mirror is replaced with a layer of plasmonic Ag nanoislands. The naturally random spatial distribution of clusters and nanoparticles formed by this deposition technique constitutes the manufacturer-resistant nanoscale morphological fingerprint of the proposed PUF. The presence of Ag nanoislands allows us to tailor the interplay between the photonic and plasmonic modes to achieve two additional security levels. The first one is constituted by the chromatic response and broad iridescence of our structures, while the second by their rich spectral response, accessible even through a common smartphone lightemitting diode. We demonstrate that the proposed architectures could also be used as an irreversible and quantitative temperature exposure label. The proposed PUFs are inexpensive, chip-to-wafer-size scalable, and can be deposited over a variety of substrates. They also hold a great promise as an encryption framework envisioning morpho-cryptography applications.

Organic Light‐Emitting Physically Unclonable Functions

“…The design and development of novel encoded surfaces are of great research interest in today's world for use in anti-counterfeiting and authentication applications. Although the majority of encoded surface applications relate to the prevention of light, [20,21] carbon nanotubes, [22] spherical [23,24] and rod shaped [25] plasmonic nanoparticles, silver nanoislands, [26] core-shell nanoparticles, [27] polymeric particles, [28] diamonds, [29] and fluorescent compounds. [30] For the development of PUFs, fluorescent compounds are particularly interesting because they allow for rapid and simple authentication with multiple and interactive challenge-response pairs using facile and well-developed spectroscopic/microscopic techniques and portable tools.…”

“…[ 9 ] Starting from the seminal work by Pappu et al., [ 6 ] optical PUF systems have been an active research area. [ 10–17 ] In the past decade, a range of material types and manufacturing routes have been studied to demonstrate PUFs using silica microparticles, [ 6 ] inherent randomness of surfaces, [ 18,19 ] randomly positioned scatterers challenged by quantum states of light, [ 20,21 ] carbon nanotubes, [ 22 ] spherical [ 23,24 ] and rod shaped [ 25 ] plasmonic nanoparticles, silver nanoislands, [ 26 ] core‐shell nanoparticles, [ 27 ] polymeric particles, [ 28 ] diamonds, [ 29 ] and fluorescent compounds. [ 30 ]…”

Triplet–triplet annihilation upconversion combined with afterglow phosphors for multi-dimensional anti-counterfeiting and encoding

“…As a result, advanced luminescent materials with unconventional excitation and emission modes including long-afterglow, 15 photon upconversion, 16,17 stimuli-responsive luminescence, 18 etc. 19,20 have been required for multidimensional anti-counterfeiting with high security levels. [21][22][23] Besides anti-counterfeiting, long-afterglow (also called longpersistent) luminescence has also been applied in bioimaging, sensing, emergency lighting and information storage 24,25 due to the self-sustain luminescence feature.…”

“…As a result, advanced luminescent materials with unconventional excitation and emission modes including long-afterglow, 15 photon upconversion, 16,17 stimuli-responsive luminescence, 18 etc. 19,20 have been required for multi-dimensional anti-counterfeiting with high security levels. 21–23…”

Quantifying the Sensitivity and Unclonability of Optical Physical Unclonable Functions

“…By using passive or active materials of different nature (integrated light sources in dielectric or metallic systems), and by playing with the systems' dimensionality (2D or 3D), a large variety of optical PUFs can be conceived, as research in the last decades has demonstrated. This includes PUFs based on organic nano-emitters 21,22 , chip-scale laser 23 , thin random scattering layers of plasmonic nano-particles [24][25][26][27] , random silver nano-structures 28,29 , or even PUFs architecture compatible with microfabrication technologies for photonic integrated circuits (PIC) [30][31][32] . In the end, any material with random structure, defects or scattering elements, including regular paper 33 , will generate complex speckle patterns when illuminated by a coherent source, making optical PUFs a highly efficient, inexpensive and robust platform for secure authentication 5,8,28,34,35 .…”