Lithography-Free Plasmonic Color Printing with Femtosecond Laser on Semicontinuous Silver Films

Abstract

Plasmonic color printing with semicontinuous metal films is a lithography-free and environment-friendly method for generating non-fading bright colors. Such films are comprised of islands -metal nanoparticles and their clusters of various dimensions, which resonate at different wavelengths upon external light illumination depending on the size and 2 shape of the local particle structures. To experimentally realize systems that were optimized for achieving a broad color range and increased stability, various silver semicontinuous metal films were deposited on a metallic (Ag) mirror with a sub-wavelength-thick dielectric (SiO2) spacer. Femtosecond laser post-processing was then introduced to extend the color gamut through spectrally induced changes from blue to green, red, and yellow. Long-term stability and durability of the structures were addressed to enable non-fading colors with an optimized overcoating dielectric layer. The thickness of the proposed design is on the order of 100 nanometers, and it can be deposited on any substrate. These structures generate a broad range of long-lasting colors in reflection that can be applied to real-life artistic or technological applications with a spatial resolution on the order of 0.3 mm or less.

Resonant Laser Printing of Optical Metasurfaces

“…Nature provides numerous examples of bright coloration from self-organized photonic crystals . Structural color based on individual resonators, such as plasmonic and dielectric nanoantennas, allows for color printing with subdiffraction resolution. − As an alternative method to liquid crystal enabled tuning of plasmonic metasurfaces, , laser printing is a cost-effective postprocessing technique that can tune the plasmonic colors of nanostructure arrays produced by nanofabrication techniques. ,, In contrast, the RLP induced self-organized metasurfaces presented here offer subwavelength resolution without lithography, and it is easy to upscale for large-volume production. To demonstrate the printing resolution of a self-organized structure that can be laser-induced, we pattern an image using the same micron-sized laser focus spot (2–4 μm) and a subdiffraction-limited step size (250 nm) but digitally varied doses according to the gray-scale depth of the image.…”

Plasmonic Color Printing via Bottom-Up Laser-Induced Photomodification Process

“…26 The Ag NPs present in the OM solution were modified by laser irradiation, resulting in various sizes and shapes of Ag NPs according to the processing conditions. The size and shape control of these Ag NPs can shift the reflectance dip of plasmonic NP structure; 19,22 thus, various colors can be realized simply through process control. Moreover, the relatively weak particle-to-particle bonding of the unpatterned regions aids easy removal thereof by an organic solvent.…”

“…18 From the different chemical and optical properties of the additional layer, improved performance can be achieved with a simple pretreatment. Since oxidation-induced degradation can also occur in plasmonic printing based on Ag NPs, 19 the application of an additional layer will be the focus of future work for stable printing with the expanded color span. Scanning electron microscopy (SEM) measurements confirmed that this coloration was caused due to the morphological variations in the laser-induced Ag nanoseeds.…”

“…This gradual fragmentation is in accordance with the previously reported photomodification of the Ag thin film. 19 During the laser modification process of the Ag layer, the reflectance dip is known to shift toward shorter wavelengths owing to the gradual fragmentation and reshaping of Ag NPs with increased fluence. 16,19,35 Vacuumdeposited Ag thin layers (<10 nm) usually have an Ag NP structure instead of that of an Ag film, because of the relatively short deposition time.…”

Large‐Scale, Panchromatic Structural Color Manipulation via Thermal Trimming

“…Over the last decade, structural color based on photonic structures has attracted extensive attention due to high resolution, [ 1,2 ] strong stability, [ 3–5 ] and easy production of compact monolithically integrated devices, [ 6,7 ] These attributes have rendered structural colors of great interest to printing, [ 1,2 ] display, [ 8,9 ] imaging, [ 10,11 ] decoration, [ 12,13 ] colorimetric sensing, [ 14–17 ] and more importantly, anti‐counterfeiting, [ 9 ] and encryption, [ 18–20 ] Many methods have produced vivid structural colors such as multilayer interference, [ 21–25 ] photonic crystals, [ 26 ] guided mode resonances, [ 27 ] plasmonic resonances, [ 12,28,29 ] and Mie scattering. [ 6,30 ] Especially, thin‐film‐based structural colors such as metal‐insulator‐me`tal (MIM) cavities, [ 8 ] lossy film cavities, [ 23 ] and multilayer [ 21 ] film systems have been implemented for the simplest fabrication and integration on a large scale.…”