Directional excitation of surface plasmons by dielectric resonators

An important aim of current research on plasmonics is to develop compact components to manipulate surface plasmon polaritons (SPPs) and specifically to develop efficient SPP couplers. The commonly used metallic resonators are inefficient to couple free-space waves to SPPs and metallic gratings require oblique incidence for achieving unidirectional propagation. In this article, we propose to use nanoscale nonuniform arrays of dielectric resonator antennas (DRAs) to realize unidirectional launching of SPPs. DRAs are made of low-loss high-permittivity nanostructures operating on a metal surface. The applications of metallodielectric nanostructures can produce resonances mainly in the low-loss dielectric parts and hence the power dissipated through oscillating current in metal can be reduced. Similar to metallic resonators, DRAs operating near resonance can provide phase control when coupling incident waves into SPPs, adding degrees of freedom in controlling propagation direction. The theoretical analysis in this article, with numerical validation, shows efficient SPPs launching by nonuniform array of cylindrical DRAs into a predesigned direction. Furthermore, with proper patterning, optimal launching can be achieved by avoiding power leakage via deflection into free space. The SPP launching condition and the influence of propagation loss are also mathematically analyzed from the viewpoint of antenna array theory. The SPPs launchers based on DRAs have a potential for applications in highly efficient integrated optics and optical waveguides.C. Fumeaux acknowledges the Australian Research Council (ARC) Future Fellowship funding scheme for support under Grant No. FT100100585

Multiresponsive Dielectric Metasurfaces Based on Dual Light‐ and Temperature‐Responsive Copolymers

Abstract Tunability is essential for unlocking a range of practical applications of high‐efficiency metasurface‐based nanophotonic devices and systems. Increased research efforts in this area during recent years led to significant progress regarding tuning mechanisms, speed, and diverse active functionalities. However, so far almost all the demonstrated works are based on a single type of physical stimulus, thereby excluding important opportunities to enhance the modulation range of the metadevices, the available design options, as well as interaction channels between the metadevices and their environment. In this article, it is experimentally demonstrated that multi‐responsive metasurfaces can be realized by combining asymmetric, highly resonant metasurfaces with multi‐responsive polymeric materials. The respective copolymers combine light‐ and temperature‐responsive comonomers in an optimized ratio. This work demonstrates clearly reversible light‐responsive, temperature‐responsive, and co‐responsive tuning of the metasurface optical resonance positions at near‐infrared wavelengths, featuring maximum spectral resonance shifts of nearly twice the full‐width‐at‐half‐maximum and accompanied by more than 60% absolute modulation in transmittance. This work provides new design freedom for multifunctional metadevices and can potentially be expanded to other types of copolymers as well. Furthermore, the studied hybrid multiresponsive systems are promising candidates for multi‐dimensional sensing applications.Light and temperature‐responsive polymers are integrated with asymmetric silicon metasurfaces for dual‐responsive tuning of their transmittance. Reversible resonance shifts induced by light exposure, temperature changes or a combination of both stimuli are experimentally demonstrated. This work paves the way for multiresponsive metasurface components and is promising for multi‐dimensional interactive smart optical devices. imag

Optically-Induced Antiferromagnetic Order in Mie-Resonant Dielectric Metasurfaces

We study silicon-based metasurfaces with complex unit cells composed of Mie-resonant dielectric nanodisks and nanorings and observe experimentally a signature of optical response with a staggered structure of optically-induced magnetic dipole moments, associated with the so-called optical antiferromagnetic order.The authors acknowledge a financial support from the Thuringian State Government within its ProExcellence Initiative (ACP2020), and the German Research Foundation DFG (STA 1426/2-1; project number 27 87 47 906). YK acknowledges a financial support from the Australian Research Council, the Alexander von Humboldt Foundation, and the Strategic Fund of the Australian National University, and also useful discussions with B. Lukyanchuk

Optical metasurfaces based on nano-scale dielectric resonators

This thesis summarises my PhD research towards applying nano-scale dielectric resonators (DRs) to optical metasurfaces for achieving various functionalities, high efficiency, and reconfigurability. Additionally, the thesis also provides brief introductions to dielectric resonator antennas, plasmonics, and a short review of optical metasurfaces. The major contributions are briefly summarised as follows: In Chapter 3, resonance properties of cylindrical nano-scale DRs on metallic substrates are analysed. At optical frequencies, subwavelength DRs with metallic substrates can support horizontal magnetic dipole resonance, which can be used for efficient coupling of surface plasmons. However, two types of resonance breakdown can occur in such DRs, and the cause for both types are analysed in detail. Of particular interest is the negatively-matched resonance breakdown, which occurs when real parts of the permittivities of a DR and its metallic substrate are negatively matched. The negatively-matched resonance breakdown is undesired for optical metasurfaces and can be avoided by inserting a low-permittivity dielectric spacer between the DR and its metallic substrate. In Chapter 4, unidirectional launching of surface plasmons based on non-uniform arrays of DRs is proposed and investigated. By comparing the principles of DR-based anomalous reflection and surface plasmon unidirectional launching, it is concluded that the optimal launching can be achieved by avoiding the first-order diffraction. The optimal launching condition is verified with numerical simulations and linear array theory. In Chapter 5, a narrowband plasmonic absorber made of a uniform array of nano-scale DRs on metallic substrates is experimentally demonstrated at visible frequencies. It relies on the surface plasmon standing waves coupled by the locally resonant nano-scale DRs for the high absorption. The simulation and measurement results are presented and analysed with coupled mode theory. In Chapter 6, a mechanically tunable DR metasurface is experimentally demonstrated at visible frequencies. The tunable metasurface is realised by embedding a uniform array of DRs into an elastomeric encapsulation. The transmission responses of the metasurface can be tuned when the encapsulation is deformed with an external strain. Measurement results confirm the predictions of simulations and shows a remarkable tuning range. A Lagrangian model is developed to rigorously analyse the simulation and measurement results. Such a design provides a preliminary concept usable in reconfigurable optical devices, and after further development can also be potentially commercialised for smart contact lenses. In Chapter 7, metasurfaces made of metal-loaded DR arrays are proposed to realise the functionality of selective thermal emission. Two metasurface designs are presented. The first design is based on a uniform array of square metal-loaded DRs, which are made of doped silicon. Theoretical and numerical analysis demonstrate stable emission peaking at nearly 8 μm across a wide temperature range. The second further-developed thermal emission metasurface is designed to have broadband emission from 8 to 13 μm atmosphere window range and low emission at all other wavelengths. In this way, it can realise the function of radiative cooling. These studies along with corresponding simulations or experimental validations demonstrate various functionalities can be realised with DR metasurfaces at optical frequencies. Furthermore, these nanostructure designs suggest a promising route for achieving the next generation highly-efficient integrated optical systems based on nano-scale DRs.Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2017

Fracture analysis of the circulating pump bolts

The microstructure, micrograph of the fracture sections and the alloy elements distribution of the fractured flange-connecting bolts of 3# circulating pump in a power plant were analyzed by the scanning electron microscopy, the optical microscopy and the electron probe microanalysis. The results showed that the failed bolts’ material is not the design material, and failure of the bolts is due to the stress corrosion crack propagation of the bolts’ austenitic material by chloride ions in seawater

Chem.-Eur. J.

We present a general strategy to nanoengineer protein-based colloidal spheres (biomimetic protocells) as versatile delivery carriers with stimuli responsiveness by the electrostatic assembly of binary components (proteins and polypeptides) in association with intermolecular disulfide cross-linking. The size of the colloidal spheres, ranging from nanoscale to microscale, is readily tuned through parameters like protein and polypeptide concentration, the ratio between both, pH, and so on. Moreover, such colloidal spheres show versatile encapsulation of various guest molecules including small organic molecules and biomacromolecules. The pH and redox dual-responsiveness facilitates the rapid release of the payload in an acidic and reductant-enriched ambient such as in lysosomes. Thus, nanoengineering of protein-based biomimetic protocells opens a new alternative avenue for developing delivery vehicles with multifunctional properties towards a range of therapeutic and diagnostic applications.We present a general strategy to nanoengineer protein-based colloidal spheres (biomimetic protocells) as versatile delivery carriers with stimuli responsiveness by the electrostatic assembly of binary components (proteins and polypeptides) in association with intermolecular disulfide cross-linking. The size of the colloidal spheres, ranging from nanoscale to microscale, is readily tuned through parameters like protein and polypeptide concentration, the ratio between both, pH, and so on. Moreover, such colloidal spheres show versatile encapsulation of various guest molecules including small organic molecules and biomacromolecules. The pH and redox dual-responsiveness facilitates the rapid release of the payload in an acidic and reductant-enriched ambient such as in lysosomes. Thus, nanoengineering of protein-based biomimetic protocells opens a new alternative avenue for developing delivery vehicles with multifunctional properties towards a range of therapeutic and diagnostic applications

Inferring circRNA-drug sensitivity associations via dual hierarchical attention networks and multiple kernel fusion

Abstract Increasing evidence has shown that the expression of circular RNAs (circRNAs) can affect the drug sensitivity of cells and significantly influence drug efficacy. Therefore, research into the relationships between circRNAs and drugs can be of great significance in increasing the comprehension of circRNAs function, as well as contributing to the discovery of new drugs and the repurposing of existing drugs. However, it is time-consuming and costly to validate the function of circRNA with traditional medical research methods. Therefore, the development of efficient and accurate computational models that can assist in discovering the potential interactions between circRNAs and drugs is urgently needed. In this study, a novel method is proposed, called DHANMKF , that aims to predict potential circRNA-drug sensitivity interactions for further biomedical screening and validation. Firstly, multimodal networks were constructed by DHANMKF using multiple sources of information on circRNAs and drugs. Secondly, comprehensive intra-type and inter-type node representations were learned using bi-typed multi-relational heterogeneous graphs, which are attention-based encoders utilizing a hierarchical process. Thirdly, the multi-kernel fusion method was used to fuse intra-type embedding and inter-type embedding. Finally, the Dual Laplacian Regularized Least Squares method (DLapRLS) was used to predict the potential circRNA-drug sensitivity associations using the combined kernel in circRNA and drug spaces. Compared with the other methods, DHANMKF obtained the highest AUC value on two datasets. Code is available at https://github.com/cuntjx/DHANMKF

Electrical Tuning of Dielectric Metasurfaces at Visible Frequencies Facilitated by Photoalignment of Liquid Crystals

We experimentally demonstrate the use of photoalignment materials for liquid-crystal based electrical tuning of resonant silicon metasurfaces with a 67% modulation depth at visible frequencies.This research was in part funded by the German Ministry of Education and Research under the project identifier 13N14147; responsibility for the content of this work resides with the author. Financial support by the Thuringian State Government within its ProExcellence initiative (ACP2020), by the German Research Foundation (STA 1426/2-1), and by the German Academic Exchange Service (Project-ID 57318571) is also gratefully acknowledged