Large-scale high purity and brightness structural color generation in layered thin film structures via coupled cavity resonance.

Structural colors, resulting from the interaction of light with nanostructured materials rather than pigments, present a promising avenue for diverse applications ranging from ink-free printing to optical anti-counterfeiting. Achieving structural colors with high purity and brightness over large areas and at low costs is beneficial for many practical applications, but still remains a challenge for current designs. Here, we introduce a novel approach to realizing large-scale structural colors in layered thin film structures that are characterized by both high brightness and purity.

Broad-Spectrum Ultrathin-Metal-Based Oxide/Metal/Oxide Transparent Conductive Films for Optoelectronic Devices.

High-quality transparent conductive materials are beneficial to improve the charge transfer and light transmittance and reduce the interface defects as well as the production cost of optoelectronic devices. A high threshold thickness of metal layer in oxide/metal/oxide (OMO) compound thin films leads to strong reflectance, especially in the near-infrared region, limiting the broad-spectrum device applications. Here, we propose a novel Zn doping strategy using the low-cost single-target sputtering technology to achieve the growth of Ag-Zn thin films (i.

Ultrathin-metal-film-based transparent electrodes with relative transmittance surpassing 100.

Flexible transparent electrodes are in significant demand in applications including solar cells, light-emitting diodes, and touch panels. The combination of high optical transparency and high electrical conductivity, however, sets a stringent requirement on electrodes based on metallic materials. To obtain practical sheet resistances, the visible transmittance of the electrodes in previous studies is typically lower than the transparent substrates the electrode structures are built on, namely, the transmittance relative to the substrate is <100%.

Transparent Perfect Microwave Absorber Employing Asymmetric Resonance Cavity.

The demand for high-performance absorbers in the microwave frequencies, which can reduce undesirable radiation that interferes with electronic system operation, has attracted increasing interest in recent years. However, most devices implemented so far are opaque, limiting their use in optical applications that require high visible transparency. Here, a scheme is demonstrated for microwave absorbers featuring high transparency in the visible range, near-unity absorption (≈99.

Optical Device Based on a Nanopillar Array by the Pattern Transfer of an Anodic Aluminum Oxide Membrane.

A simple and convenient nanofabrication method is proposed to achieve nanopillar arrays by the pattern transfer of an anodic aluminum oxide membrane, profiting from the rapid and efficient preparation process and regular hexagonal lattice patterns of the anodic aluminum oxide template. The taper angle of the nanopillar is affected by the distribution of the vapor particles during the deposition process, which is highly dependent on the material and deposition power. Based on this method, a novel scheme employing aluminum nanopillar arrays is demonstrated to realize the color tuning feature by simply varying the thickness of the top dielectric layer within a large range.

Electrodeposition of Large Area, Angle-Insensitive Multilayered Structural Colors.

We demonstrate structural colors produced by a simple, inexpensive, and nontoxic electrodeposition process. Asymmetric metal-dielectric-metal (MDM) multilayered structures were achieved by sequential electrodeposition of smooth gold, thin cuprous oxide, and finally thin gold on conductive substrates, forming an effective optical cavity with angle-insensitive characteristics. Different colors of high brightness were achieved by simply tuning the thickness of the electrodeposited middle cavity layer.

High-Performance Large-Scale Flexible Optoelectronics Using Ultrathin Silver Films with Tunable Properties.

One key obstacle in fabricating efficient flexible and printable optoelectronic devices is the absence of ideal flexible transparent conductors with superior optical, electrical, and mechanical properties. Here, high-performance flexible transparent conductors are demonstrated using ultrathin (<10 nm) doped silver films, which exhibit an averaged visible transmittance of 80% without any antireflection coating, sheet resistance less than 20 Ω sq, and mechanical stability over 1000 bending cycles. The conductor is prepared by doping silver with an additive metal (e.

Highly Transparent and Broadband Electromagnetic Interference Shielding Based on Ultrathin Doped Ag and Conducting Oxides Hybrid Film Structures.

Reducing electromagnetic interference (EMI) across a broad radio frequency band is crucial to eliminate adverse effects of increasingly complex electromagnetic environment. Current shielding materials or methods suffer from trade-offs between optical transmittance and EMI shielding capability. Moreover, poor mechanical flexibility and fabrication complexity significantly limit their further applications in flexible electronics.

High-color-purity, angle-invariant, and bidirectional structural colors based on higher-order resonances.

Structural colors with high color purity and low fabrication cost are highly desired in a wide variety of applications including displays, light emitting diodes, decorations, and optical detections. Here, we demonstrate a semitransparent pentalayer structure for creating angle-insensitive, high-purity reflective colors that exploit a higher-order cavity resonance. Moreover, the designed structure in a symmetric configuration presents bright and saturated colors from both directions with a high efficiency up to 85% and a high angular tolerance up to ±60°.

Visualizing Mie Resonances in Low-Index Dielectric Nanoparticles.

Resonant light scattering by metallic and high-index dielectric nanoparticles has received enormous attention and found many great applications. However, low-index dielectric nanoparticles typically do not show resonant scattering behaviors due to poor light confinement caused by small index contrast. This Letter describes a simple and effective approach to drastically enhance the resonance effect of the low-index particles by partial metal dressing.

Robust Extraction of Hyperbolic Metamaterial Permittivity using Total Internal Reflection Ellipsometry.

Hyperbolic metamaterials are optical materials characterized by highly anisotropic effective permittivity tensor components having opposite signs along orthogonal directions. The techniques currently employed for characterizing the optical properties of hyperbolic metamaterials are limited in their capability for robust extraction of the complex permittivity tensor. Here we demonstrate how an ellipsometry technique based on total internal reflection can be leveraged to extract the permittivity of hyperbolic metamaterials with improved robustness and accuracy.

High-Performance Doped Silver Films: Overcoming Fundamental Material Limits for Nanophotonic Applications.

The field of nanophotonics has ushered in a new paradigm of light manipulation by enabling deep subdiffraction confinement assisted by metallic nanostructures. However, a key limitation which has stunted a full development of high-performance nanophotonic devices is the typical large losses associated with the constituent metals. Although silver has long been known as the highest quality plasmonic material for visible and near infrared applications, its usage has been limited due to practical issues of continuous thin film formation, stability, adhesion, and surface roughness.

Invisibility cloak with image projection capability.

Investigations of invisibility cloaks have been led by rigorous theories and such cloak structures, in general, require extreme material parameters. Consequently, it is challenging to realize them, particularly in the full visible region. Due to the insensitivity of human eyes to the polarization and phase of light, cloaking a large object in the full visible region has been recently realized by a simplified theory.