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Dima Bolmatov, Mikhail Zhernenkov, Lewis Sharpnack, Dena M Agra-Kooijman, Satyendra Kumar, Alexey Suvorov, Ronald Pindak, Yong Q Cai, Alessandro Cunsolo
The investigation of phononic collective excitations in soft matter systems at the molecular scale has always been challenging due to limitations of experimental techniques in resolving low-energy modes. Recent advances in Inelastic X-ray Scattering (IXS) enabled the study of such systems with unprecedented spectral contrast at meV excitation energies. In particular, it has become possible to shed light on the low-energy collective motions in materials whose morphology and phase behavior can easily be manipulated, such as mesogenic systems...
May 26, 2017: Nano Letters
Sergey M Novikov, Vladimir N Popok, Andrey B Evlyukhin, Muhammad Hanif, Per Morgen, Jacek Fiutowski, Jonas Beermann, Horst-Guenter Rubahn, Sergey I Bozhevolnyi
: Plasmonics sensor configurations utilizing localized plasmon resonances in silver nanostructures typically suffer from rapid degradation of silver in ambient atmospheric conditions. In this work, we report on the fabrication and detailed characterization of ensembles of monocrystalline silver nanoparticles (NPs), which exhibit a long-term stability of optical properties under ambient conditions without any protective treatments. Ensembles with different densities (surface coverages) of size-selected NPs (diameters from 12...
May 25, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Tomer Lewi, Hayden A Evans, Nikita A Butakov, Jon A Schuller
Subwavelength Mie resonators have enabled new classes of optical antenna and nanophotonic devices and can act as the basic meta-atoms constituents of low-loss dielectric metasurfaces. In any application, tunable Mie resonances are key to achieving dynamic and reconfigurable operation. However, active tuning of these nanoantennas is still limited and usually results in sub-linewidth resonance tuning. Here, we demonstrate ultra-wide dynamic tuning of PbTe Mie resonators fabricated via both laser ablation and a novel solution-processing approach...
May 25, 2017: Nano Letters
Youngseop Lee, Sang-Gil Park, SeokJae Yoo, Minhee Kang, Sang Chul Jeon, Young-Su Kim, Q-Han Park, Ki-Hun Jeong
We report an optically patternable metamaterial (OPM) for ultraviolet nanolithography below the diffraction limit. The OPM features monolayered silver nanoislands embedded within a photosensitive polymer by using spin-coating of an ultrathin polymer, oblique angle deposition and solid-state embedment of silver nanoislands. This unique configuration simultaneously exhibits both negative effective permittivity and high image contrast in the ultraviolet range, which enables the surface plasmon excitation for the clear photolithographic definition of minimum feature size of 70 nm (< ~ λ/5) beyond the near-field zone...
May 24, 2017: ACS Applied Materials & Interfaces
A V Kondratov, O Y Rogov, R V Gainutdinov
A significant part of the optical metamaterial phenomena has the plasmonic nature and their investigation requires very accurate knowledge of the fabricated structures shape with a focus on the periodical features. We describe a consistent approach to the shape reconstruction of the plasmonic nanostructures. This includes vertical and tilted spike AFM probes fabrication, AFM imaging and specific post-processing. We studied a complex-shaped chiral metamaterial and conclude that the described post-processing routine extends possibilities of the existing deconvolution algorithms in the case of periodical structures with known rotational symmetry, by providing valuable information about periodical features...
May 11, 2017: Ultramicroscopy
Tengfeng Zhu, Yihan Zhou, Yijie Lou, Hui Ye, Min Qiu, Zhichao Ruan, Shanhui Fan
Optical analog computing offers high-throughput low-power-consumption operation for specialized computational tasks. Traditionally, optical analog computing in the spatial domain uses a bulky system of lenses and filters. Recent developments in metamaterials enable the miniaturization of such computing elements down to a subwavelength scale. However, the required metamaterial consists of a complex array of meta-atoms, and direct demonstration of image processing is challenging. Here, we show that the interference effects associated with surface plasmon excitations at a single metal-dielectric interface can perform spatial differentiation...
May 19, 2017: Nature Communications
Xu Chen, Wenhui Fan
A planar terahertz metamaterial sensor consisting of a corrugated metal stripe perforated by three rectangular grooves is proposed and investigated numerically. Due to the formation of Fabry-Perot resonance of the spoof surface plasmons mode on the corrugated metal stripe, the extremely sharp resonance in transmission spectrum associated with strong local field enhancement and high quality factor can be realized and exploited for ultrasensitive sensing. Since the intense interaction between electromagnetic waves and analyte materials, the frequency sensitivity of 1...
May 18, 2017: Scientific Reports
Xiaoliang Ma, Mingbo Pu, Xiong Li, Yinghui Guo, Ping Gao, Xiangang Luo
Chiral metamaterials represent a special type of artificial structures that cannot be superposed to their mirror images. Due to the lack of mirror symmetry, cross-coupling between electric and magnetic fields exist in chiral mediums and present unique electromagnetic characters of circular dichroism and optical activity, which provide a new opportunity to tune polarization and realize negative refractive index. Chiral metamaterials have attracted great attentions in recent years and have given rise to a series of applications in polarization manipulation, imaging, chemical and biological detection, and nonlinear optics...
May 17, 2017: Nanomaterials
Zeang Zhao, Jiangtao Wu, Xiaoming Mu, Haosen Chen, H Jerry Qi, Daining Fang
Origami structures are of great interest in microelectronics, soft actuators, mechanical metamaterials, and biomedical devices. Current methods of fabricating origami structures still have several limitations, such as complex material systems or tedious processing steps. We present a simple approach for creating three-dimensional (3D) origami structures by the frontal photopolymerization method, which can be easily implemented by using a commercial projector. The concept of our method is based on the volume shrinkage during photopolymerization...
April 2017: Science Advances
Xu Chen, Wenhui Fan
A planar terahertz metamaterial consisting of square split ring resonators is proposed, and the excitation of toroidal dipolar resonance is demonstrated. Moreover, we theoretically investigate the strong interaction between graphene and toroidal dipolar resonance of the metamaterial. By varying its Fermi energy, the simulations show that graphene can actively modulate the transmission amplitude of toroidal dipolar resonance and even switch it off. The interaction of the toroidal dipolar resonance with monolayer graphene further highlights the ultrasensitive sensing characteristic of the planar metamaterial, which can be utilized for other graphene-like two-dimensional materials...
May 15, 2017: Optics Letters
Rita Schmidt, Alexey Slobozhanyuk, Pavel Belov, Andrew Webb
Developments in metamaterials and related structures such as metasurfaces have opened up new possibilities in designing materials and devices with unique properties. Here we report a new hybrid metasurface structure, comprising a two-dimensional metamaterial surface and a very high permittivity dielectric substrate, that has been designed to enhance the local performance of an ultra-high field MRI scanner. This new flexible and compact resonant structure is the first metasurface which can be integrated with multi-element close-fitting receive coil arrays that are used for all clinical MRI scans...
May 10, 2017: Scientific Reports
Jie Li, Ming-Jie Zhu, Ying-Hua Wang, Ren-Chao Jin, Jia-Qi Li, Zheng-Gao Dong
The far-field radiation of a single dipolar emitter can be controlled by coupling to toroidal dipole resonance attached to metallic double flat rings, realizing a conversion from non- to super-radiating. The underlying physical mechanism is the hybridization interference of toroidal and electric dipoles under an asymmetric configuration by introducing a radial displacement of the dipolar emitter. By embedding gain medium in the gap spacer between double flat rings, the directional far-field super-radiating power can achieve a tremendous enhancement with a moderate requirement on the gain coefficient, promoting light-matter interaction manipulation...
May 9, 2017: Scientific Reports
Ankit Srivastava, John R Willis
All metamaterial applications are based upon the idea that extreme material properties can be achieved through appropriate dynamic homogenization of composites. This homogenization is almost always done for infinite domains and the results are then applied to finite samples. This process ignores the evanescent waves which appear at the boundaries of such finite samples. In this paper, we first clarify the emergence and purpose of these evanescent waves in a model problem consisting of an interface between a layered composite and a homogeneous medium...
April 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
Zuojia Wang, Liqiao Jing, Kan Yao, Yihao Yang, Bin Zheng, Costas M Soukoulis, Hongsheng Chen, Yongmin Liu
Origami is the art of folding two-dimensional (2D) materials, such as a flat sheet of paper, into complex and elaborate three-dimensional (3D) objects. This study reports origami-based metamaterials whose electromagnetic responses are dynamically controllable via switching the folding state of Miura-ori split-ring resonators. The deformation of the Miura-ori unit along the third dimension induces net electric and magnetic dipoles of split-ring resonators parallel or anti-parallel to each other, leading to the strong chiral responses...
May 8, 2017: Advanced Materials
Yi Tian, Francisco Pelayo García de Arquer, Cao-Thang Dinh, Gael Favraud, Marcella Bonifazi, Jun Li, Min Liu, Xixiang Zhang, Xueli Zheng, Md Golam Kibria, Sjoerd Hoogland, David Sinton, Edward H Sargent, Andrea Fratalocchi
The direct conversion of solar energy into fuels or feedstock is an attractive approach to address increasing demand of renewable energy sources. Photocatalytic systems relying on the direct photoexcitation of metals have been explored to this end, a strategy that exploits the decay of plasmonic resonances into hot carriers. An efficient hot carrier generation and collection requires, ideally, their generation to be enclosed within few tens of nanometers at the metal interface, but it is challenging to achieve this across the broadband solar spectrum...
May 8, 2017: Advanced Materials
Frances Morgan, Antony Murphy, William Hendren, Gregory Wurtz, Robert J Pollard
An in situ transmission-based system has been designed to optically monitor the ellipsometry constants of a hyperbolic plasmonic metamaterial during electrochemical growth. The metamaterial, made from an array of vertically aligned gold nanorods, has demonstrated an unprecedented ability to manipulate the polarization of light using subwavelength thickness slabs, making in situ ellipsometric data a powerful tool in the controlled design of such components. In this work, we show practical proof-of-principle of this design method and rationalize the ellipsometric output on the basis of the modal properties of the nanorod metamaterial...
May 10, 2017: ACS Applied Materials & Interfaces
Yongzheng Wen, Ji Zhou
A purely artificial mechanism for optical nonlinearity is proposed based on a metamaterial route. The mechanism is derived from classical electromagnetic interaction in a metamolecule consisting of a cut-wire meta-atom nested within a split-ring meta-atom. Induced by the localized magnetic field in the split-ring meta-atom, the magnetic force drives an anharmonic oscillation of free electrons in the cut-wire meta-atom, generating an intrinsically nonlinear electromagnetic response. An explicit physical process of a second-order nonlinear behavior is adequately described, which is perfectly demonstrated with a series of numerical simulations...
April 21, 2017: Physical Review Letters
Longqing Cong, Prakash Pitchappa, Chengkuo Lee, Ranjan Singh
Controlling the phase of local radiation by using exotic metasurfaces has enabled promising applications in a diversified set of electromagnetic wave manipulation such as anomalous wavefront deflection, flat lenses, and holograms. Here, we theoretically and experimentally demonstrate an active phase transition in a micro-electromechanical system-based metadevice where both the phase response and the dispersion of the metamaterial cavity are dynamically tailored. The phase transition is determined by the radiative and the absorptive losses in a metal-insulator-metal cavity that obeys the coupled-mode theory...
May 4, 2017: Advanced Materials
Arijit Bardhan Roy, Sonali Das, Avra Kundu, Chandan Banerjee, Nillohit Mukherjee
Herein, we report the fabrication of flexible solar cells based on a crystalline p-Si/n-ZnO heterostructure for the first time. An enhancement of ∼52% in the base efficiency was achieved by the application of spherical SiO2 nanoparticles as light trapping structures on the top. The use of ZnO not only offers a facile route of synthesis, but also provides an additional advantage of large band bending, leading to notable open circuit voltage and formation of an intermediate ultra-thin barrier layer of Zn2SiO4 for minimized carrier recombination...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Zheping Shao, Yihao Yang, Zuojia Wang, Muhiddeen Yahaya, Bin Zheng, Shahram Dehdashti, Huaping Wang, Hongsheng Chen
Guiding surface states through disorders recently has attracted attention of scientists from diverse backgrounds. In this work, we report a robust method to guide surface plasmon polaritons (SPPs) through arbitrary distorted metal surfaces (a kind of disorder), including slopes, bumps, and sharp corners. Almost total transmissions over a broad frequency range can be achieved by use of infinitely anisotropic metamaterials (IAMs). The SPPs are coupled into and out of the bulk modes in the IAMs, where the bulk modes are routed by altering the principle axis of the IAMs...
May 1, 2017: Optics Express
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