Metasurface holography, the reconstruction of holographic images by modulating the spatial amplitude and phase of light using metasurfaces, has emerged as a next‐generation display technology. ...However, conventional fabrication techniques used to realize metaholograms are limited by their small patterning areas, high manufacturing costs, and low throughput, which hinder their practical use. Herein, a high efficiency hologram using a one‐step nanomanufacturing method with a titanium dioxide nanoparticle‐embedded‐resin, allowing for high‐throughput and low‐cost fabrication is demonstrated. At a single wavelength, a record high theoretical efficiency of 96.9% is demonstrated with an experimentally measured conversion efficiency of 90.6% and zero‐order diffraction of 7.3% producing an ultrahigh‐efficiency, twin‐image free hologram that can even be directly observed under ambient light conditions. Moreover, a broadband meta‐atom with an average efficiency of 76.0% is designed, and a metahologram with an average efficiency of 62.4% at visible wavelengths from 450 to 650 nm is experimentally demonstrated.
An ultrahigh‐efficiency hologram using a one‐step printing of a TiO2 nanoparticle‐embedded‐resin (nano‐PER) is designed and experimentally demonstrated. Record efficiencies of 96.9% and 90.6% are theoretically and experimentally realized. The extremely high efficiency allows the holographic images to be clearly observed even under ambient lighting conditions, while the one‐step nano‐PER nanoimprinting fabrication method allows the realization of high‐throughput and low‐cost metaholograms.
The optical spin Hall effect, which describes the spin-dependent and transverse shift of light, has been steadily investigated with the development of sensing applications such as ...polarization-dependent sensors, material interface analysis, and refractive index spectroscopy. However, practical optical spin Hall effect sensing platforms have not been reported since the previous reports have only focused on passive platforms. Here, we propose a biosensing platform using chitosan-coated all-dielectric metamaterials, which can detect the relative humidity of the surroundings by analyzing the displacement of the spin Hall effect. The chitosan coating provides a high sensitivity of relative humidity with a dynamic optical spin Hall effect in all-dielectric metamaterials. The maximum displacement of the split beam is calculated as 350 nm when the relative humidity changes by 60%, resulting in 8.75 nm shift per 1% of relative humidity change. This mechanism can be further exploited for a biosensing platform since the chitosan-coated all-dielectric metamaterials are biocompatible, biodegradable, and hydrophilic. Considering the chitosan-coated all-dielectric metamaterials have high feasibility with low-cost, high-throughput nanoimprinting methods, the dynamic optical spin Hall effect-based metamaterials will be a candidate of a promising real-time and ultra-sensitive sensing platform for detecting biomolecules.
We investigated the morphology of lamellae-forming polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) confined in asymmetric hemisphere nanocavities which were prepared by oblique ...angle deposition of gold with various thicknesses. When the thickness of the deposited gold layer (t Au) was 0.5L 0 of PS-b-PMMA (L 0 is the lamellar domain spacing of PS-b-PMMA in bulk), concentric lamellar patterns were formed on the top surface of the nanocavities. Interestingly, at t Au = 1L 0, WiFi-like nanopatterns were observed on the top surface. This is because of the reduction of dislocations of PS and PMMA lamellar microdomains near the center of the nanocavity. The experimentally observed morphologies are consistent with prediction by self-consistent field theory. In addition, the inner wall of the hemispherical nanocavity was modified by grafting three different polymer brushes (PS, PMMA, and PS-r-PMMA) to change the affinity to each block. When the nanocavity was grafted by PMMA, WiFi-like nanopatterns were observed. On the other hand, laterally stacked U-shaped nanopatterns were formed in a nanocavity grafted by PS-r-PMMA with neutral affinity to PS and PMMA. We also fabricated an array of silver WiFi-like nanopatterns composed of laterally stacked split-ring resonators after selective silver deposition only on the PS microdomains. They showed unique plasmonic resonances depending on the polarization angle of incident light in near-infrared (NIR) wavelengths. The nanopatterns with broken symmetry obtained in this study can be used in advanced optical devices for structural coloration and optical anticounterfeiting.
Abstract Extracting the desired information from sensor data with various internal and external effects is a significant challenge in sensor applications. Difficult‐to‐control factors such as ...temperature, humidity, and sample position can significantly affect the stability and reliability of sensor data. In this paper, a deep learning‐based glucose sensing method that is robust to variations in sample position is proposed. It is shown that the variations in sample position affect the sensor data measured by the designed split ring resonator‐based microwave sensor. Then, artificial neural network and 1D convolutional neural network (CNN) models are evaluated for extracting glucose concentration information from the sensor data measured at random sample positions. The concentration of the glucose solution ranged from 1% to 23% (2% increments). The 1D CNN with all frequencies (0.5–18 GHz) of the and datasets outperformed the other model, with a mean absolute error (MAE) of 0.695% and a mean squared error (MSE) of 0.876 evaluated via cross‐validation. The study demonstrated that the sensor system can be applied in real life by performing fruit Brix estimation based on transfer learning of the previous 1D CNN network, and the MAE and MSE are 0.450% and 0.305, respectively.
The high refractive indexes and low optical losses of dielectrics are preferred for designing highly efficient metasurfaces with unprecedented wavefront control such as near-unity numerical aperture ...metalenses and wide-angle beam spreading. Regardless of such intuitive material selections, the correlation between metasurface performance and material properties has not been clearly defined. Notwithstanding the unclear correlation, the intensity ratio of manipulated light to input beam, often called the efficiency, is an important factor for constructing various photonic applications from augmented reality to sensors. In this context, the efficiency records of the previous metasurfaces should be classified with materials aspects to understand current limitations on their efficiencies. This perspective organizes the efficiency records of metasurfaces depending on optical materials, introducing a way to engineer the optical properties of various dielectric materials to improve metasurface efficiencies. Furthermore, this perspective covers the candidates for nonlinear optical materials that can potentially be used for efficient frequency conversion.
Humidity‐responsive structural coloration is actively investigated to realize real‐time humidity sensors for applications in smart farming, food storage, and healthcare management. Here, ...humidity‐tunable nano pixels are investigated with a 700 nm resolution that demonstrates full standard RGB (sRGB) gamut coverage with a millisecond‐response time. The color pixels are designed as Fabry–Pérot (F–P) etalons which consist of an aluminum mirror substrate, humidity‐responsive polyvinyl alcohol (PVA) spacer, and a top layer of disordered silver nanoparticles (NPs). The measured volume change of the PVA reaches up to 62.5% when the relative humidity (RH) is manipulated from 20 to 90%. The disordered silver NP layer permits the penetration of water molecules into the PVA layer, enhancing the speed of absorption and swelling down to the millisecond level. Based on the real‐time response of the hydrogel‐based F–P etalons with a high‐throughput 3D nanoimprint technique, a high‐resolution multicolored color print that can have potential applications in display technologies and optical encryption, is demonstrated.
Reversible humidity‐responsive 700 nm2 full‐color pixels are demonstrated through nanoimprinting lithography. The pixel consists of a mirror, humidity‐responsive polyvinyl alcohol, and top silver nanoparticles, and demonstrates the sRGB with the relative humidity changes. Silver nanoparticles shorten the modulation speed by a millisecond due to porosity, while the effective optical properties extend the absorption bandwidth, thereby enabling vivid color.
In article number 1901932, Inkyu Park, Junsuk Rho and co‐workers introduce a tunable Fabry–Pérot resonator that has metal–(chitosan‐based hydrogel)–metal structure. The chitosan swells in response to ...changes in relative humidity; this change affects transmissive structural color of the multilayer structure. As demonstration, this tunable resonator is utilized for a real‐time colorimetric humidity sensor combined with a photovoltaic cell, which can lead to development of a self‐powered sensor.
The development of real-time and sensitive humidity sensors is in great demand from smart home automation and modern public health. We hereby proposed an ultrafast and full-color colorimetric ...humidity sensor that consists of chitosan hydrogel sandwiched by a disordered metal nanoparticle layer and reflecting substrate. This hydrogel-based resonator changes its resonant frequency to external humidity conditions because the chitosan hydrogels are swollen under wet state and contracted under dry state. The response time of the sensor is ~10
faster than that of the conventional Fabry-Pérot design. The origins of fast gas permeation are membrane pores created by gaps between the metal nanoparticles. Such instantaneous and tunable response of a new hydrogel resonator is then exploited for colorimetric sensors, anti-counterfeiting applications, and high-resolution displays.
Secure virtualised environment Chouhan, Pushpinder Kaur; Sezer, Sakir; Yangseo Choi ...
The 9th International Conference for Internet Technology and Secured Transactions (ICITST-2014),
2014-Dec.
Conference Proceeding
Cloud computing is a technological advancement that provide resources through Internet on pay-as-you-go basis. Cloud computing uses virtualisation technology to enhance the efficiency and ...effectiveness of its advantages. Virtualisation is the key to consolidate the computing resources to run multiple instances on each hardware, increasing the utilization rate of every resource, thus reduces the number of resources needed to buy, rack, power, cool, and manage. Cloud computing has very appealing features, however, lots of enterprises and users are still reluctant to move into cloud due to serious security concerns related to virtualisation layer. Thus, it is foremost important to secure the virtual environment. In this paper, we present an elastic framework to secure virtualised environment for trusted cloud computing called Server Virtualisation Security System (SVSS). SVSS provide security solutions located on hypervisor for Virtual Machines by deploying malicious activity detection techniques, network traffic analysis techniques, and system resource utilization analysis techniques. SVSS consists of four modules: Anti-Virus Control Module, Traffic Behavior Monitoring Module, Malicious Activity Detection Module and Virtualisation Security Management Module. A SVSS prototype has been deployed to validate its feasibility, efficiency and accuracy on Xen virtualised environment.
Metasurface holography, the reconstruction of holographic images by modulating the spatial amplitude and phase of light using metasurfaces, has emerged as a next-generation display technology. ...However, conventional fabrication techniques used to realize metaholograms are limited by their small patterning areas, high manufacturing costs, and low throughput, which hinder their practical use. Herein, we demonstrate a high efficiency hologram using a one-step nanomanufacturing method with a titanium dioxide nanoparticle-embedded-resin, allowing for high-throughput and low-cost fabrication. At a single wavelength, a record high 96.4% theoretical efficiency is demonstrated with an experimentally measured conversion efficiency of 90.6% and zero-order diffraction of 7.3% producing an ultrahigh-efficiency, twin-image free hologram, that can even be directly observed under ambient light conditions. Moreover, we design a broadband meta-atom with an average efficiency of 76.0% and experimentally demonstrate a metahologram with an average efficiency of 62.4% at visible wavelengths from 450 to 650 nm.
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