Metasurface-Driven Optically Variable Devices

Abstract

Optically variable devices (OVDs) are in tremendous demand as optical indicators against the increasing threat of counterfeiting. Conventional OVDs are exposed to the danger of fraudulent replication with advances in printing technology and widespread copying methods of security features. Metasurfaces, two-dimensional arrays of subwavelength structures known as meta-atoms, have been nominated as a candidate for a new generation of OVDs as they exhibit exceptional behaviors that can provide a more robust solution for optical anti-counterfeiting. Unlike conventional OVDs, metasurfacedriven OVDs (mOVDs) can contain multiple optical responses in a single device, making them difficult to reverse engineered. Well-known examples of mOVDs include ultrahighresolution structural color printing, various types of holography, and polarization encoding. In this review, we discuss the new generation of mOVDs. The fundamentals of plasmonic and dielectric metasurfaces are presented to explain how the optical responses of metasurfaces can be manipulated. Then, examples of monofunctional, tunable, and multifunctional mOVDs are discussed. We follow up with a discussion of the fabrication methods needed to realize these mOVDs, classified into prototyping and manufacturing techniques. Finally, we provide an outlook and classification of mOVDs with respect to their capacity and security level. We believe this newly proposed concept of OVDs may bring about a new era of optical anticounterfeit technology leveraging the novel concepts of nano-optics and nanotechnology.

Schrödinger’s red pixel by quasi-bound-states-in-the-continuum

“…To the best of our knowledge, the results represent the highest red saturation achieved by nanostructures with full spectral characterization across from 380 to 780 nm. Notably, because of the angle- and polarization-dependent nature of the color, the presented design could be exploited for unique visual effects that are absent in pigments for polarization encrypted anti-counterfeiting applications ( 34 ). Moreover, different configurations based on single asymmetric dielectric nanostructures could be explored further with smaller footprints toward higher printing resolution ( 31 , 54 ).…”

“…In addition, the achieved color saturation has a strong dependence on the incidence angle and polarization due to the nature of q-BIC resonances. The achieved highly saturated red could be potentially scaled up, e.g., via deep ultraviolet lithography and nano-imprint lithography ( 34 ), to reach the dimensions of reflective displays based on multilayer film configuration ( 35 ) and lead to potential applications of compact red filters ( 36 ), highly saturated reflective displays ( 22 , 37 ), nonlocal metasurfaces ( 38 ), and miniaturized spectrometers ( 39 ).…”

Tunable metasurfaces towards versatile metalenses and metaholograms: a review

“…133 Single-layer metasurfaces can realize multiple independent phase profiles, which can contain distinct information under illumination of different polarization states of light. Such metasurface holograms are actively used in optical encryption 144 and applications such as polarization analyzers. An orthogonally polarized metasurface hologram that uses the PB phase can enable direct detection of polarization states in a one-time measurement.…”

Enhancement of Luminous Intensity Emission from Incoherent LED Light Sources within the Detection Angle of 10° Using Metalenses

“…Optical metasurfaces are made up of precisely designed structures, known as meta-atoms, that can modulate the phase [ 1 , 2 ], amplitude [ 3 , 4 , 5 ], and polarization [ 6 , 7 ] of incident light. Metalenses (MLs) [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ], meta-holograms [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], structural color [ 28 , 29 , 30 , 31 ], light detection [ 32 , 33 , 34 , 35 , 36 , 37 , 38 ], perfect absorber [ 39 , 40 ], and sensors [ 41 , 42 , 43 , 44 , 45 , 46 , 47 ] are typical applications of optical metasurfaces. Recently, various improvements to MLs have been repo...…”