Capped MIM metamaterial for ultra-broadband perfect absorbing and its application in radiative cooling.

Radiative cooling, which needs no external energy to lower the temperature, has drawn great interest in recent years. As a potential candidate, the design of a metamaterial cooler remains a big challenge due to the complexity of the nanostructure and the low average absorptivity. In this work, a capped metal-insulator-metal metamaterial is proposed to achieve ultra-broadband perfect absorbing.

Exact transformation optics by using electrostatics.

We present a novel method for designing transformation optical devices based on electrostatics. An arbitrary transformation of electrostatic field can lead to a new refractive index distribution, where wavefronts and energy flux lines correspond to equipotential surfaces and electrostatic flux lines, respectively. Owing to scalar wave propagating exactly following an eikonal equation, wave optics and geometric optics share the same solutions in the devices.

All-dielectric metasurfaces with high Q-factor Fano resonances enabling multi-scenario sensing.

We propose and numerically demonstrate high Q-factor sensors based on all-dielectric metasurfaces, which are very sensitive to the change of the refractive index of the surrounding media and the incident angle. By using the light incident angular scanning method, the all-dielectric metasurface based on symmetric tetramer can act as an excellent sensing platform for trace-amount molecules such as protein A/G, 2, 4-DNT, and 2D material graphene with huge absorbance enhancement in the mid-infrared broadband spectrums. The results reveal that envelope of absorbance amplitudes is in good agreement with the vibrational mode of molecules, and absorbance enhancement factors reach as high as 10 dB in the mid-infrared wavelength range from 5.

Doubly mirror-induced electric and magnetic anapole modes in metal-dielectric-metal nanoresonators.

Anapole mode is a nonradiative resonance originating from the destructive interference between co-excited Cartesian electric dipole and toroidal dipole moments. With at least two symmetric circulating currents, the anapole mode in all-dielectric nanoresonators provides the opportunity to operate the double perfect electric conductor (PEC) mirror effects. In this work, unlike the conventional metal-dielectric-metal (MDM) nanostructure generating a plasmonic magnetic resonance, two metal components are employed to produce the fictitious images of the middle dielectric, and the whole system can thus excite the doubly mirror-induced anapole mode.

High-efficient and low-coupling spoof surface plasmon polaritons enabled by V-shaped microstrips.

We propose a novel variety of V-shaped microstrips for highly efficient and strongly confined spoof surface plasmon polaritons (SSPPs) propagation. We analyze the dispersion characteristics of the V-shaped SSPPs microstrip units and find that the asymptotic frequency of the dispersion curve can be significantly reduced by adding the folded stub without increasing the lateral dimension of the structure. The V-shaped microstrip possesses the advantage of being compatible with a conventional microstrip without the need for complicated and bulky mode conversion structures in other typical grooved SSPP waveguides.

Electrically Tunable Broadband Terahertz Absorption with Hybrid-Patterned Graphene Metasurfaces.

We numerically demonstrate a broadband terahertz (THz) absorber that is based on a hybrid-patterned graphene metasurface with excellent properties of polarization insensitivity, wide-angle, and active tunability. Our design is made up of a single-layer graphene with periodically arranged hybrid square/disk/loop patterns on a multilayer structure. We find that broadband absorption with 90% terahertz absorbance and the fractional bandwidth of 84.

Enhancing artificial sum frequency generation from graphene-gold metamolecules.

The enhanced artificial sum frequency generation (SFG) is realized by graphene-gold metamolecules at the mid-infrared without any natural nonlinear material. The unit cell of the proposed metamolecules combines an inner graphene cut-wire meta-atom and an outer gold split-ring resonator meta-atom. In order to achieve high efficiency of the artificial SFG, not only the novel material of graphene with high mobility is used as the constituent material, but also the double resonances at two fundamental frequencies are excited to form an intensive magnetic Lorentz force.

[Treatment of intercondylar fracture of the humerus through internal and external elbow approach or elbow posterior olecranon osteotomy approach].

Objective: To investigate the efficacy, advantages and disadvantages of internal and external elbow joint approach and olecranon osteotomy approach for the treatment of intercondylar fracture of humerus.

Methods: From October 2012 to May 2016, 18 cases of intercondylar fracture of humerus were treated by operation including 12 males and 6 females with a mean age of 33.5 years old (ranged from 4 to 56 years old); 8 cases were operated by internal and external elbow joint approach, 10 cases were operated by olecranon osteotomy approach.

Broadband absorber with periodically sinusoidally-patterned graphene layer in terahertz range.

We demonstrate that a broadband terahertz absorber with near-unity absorption can be realized using a net-shaped periodically sinusoidally-patterned graphene sheet, placed on a dielectric spacer supported on a metallic reflecting plate. Because of the gradient width modulation of the unit graphene sheet, continuous plasmon resonances can be excited, and therefore broadband terahertz absorption can be achieved. The results show that the absorber's normalized bandwidth of 90% terahertz absorbance is over 65% under normal incidence for both TE and TM polarizations when the graphene chemical potential is set as 0.

Strongly Confined Spoof Surface Plasmon Polaritons Waveguiding Enabled by Planar Staggered Plasmonic Waveguides.

We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated.

Independent tuning of double plasmonic waves in a free-standing graphene-spacer-grating-spacer-graphene hybrid slab.

The independent excitation and tuning of double plasmonic waves are realized in a free-standing graphene-spacer-grating-spacer-graphene (GSGSG) hybrid slab, which consists of two graphene field effect transistors placed back-to-back to each other. Resulted from the high transparency and the tight confinement of surface plasmonic mode for the graphene, double plasmonic waves can be independently excited by guided-mode resonances (GMRs). Theoretical and numerical investigations are performed in the mid-infrared band.

Subsurface nano-imaging with self-assembled spherical cap optical nanoscopy.

Frequently-used subsurface nano-imaging techniques have limitations in interference, stability, complexity, timeliness and cost reduction on account of the combination of excited ultrasound signal or probed cantilever tip. Though some improved optical methods can directly and visually obtain subsurface nanofeatures, the high refractive index difference (RID) between introduced superlens and subsurface object will inevitably degenerate the image quality. In this paper, a simple and reliable experimental technique is presented to self-assemble spherical cap optical nanoscopy (SCON) subsurface nano-imaging system (SNIS) with two low RID materials.

Power-ratio tunable dual-wavelength laser using linearly variable Fabry-Perot filter as output coupler.

For a linearly variable Fabry-Perot filter, the peak transmission wavelengths change linearly with the transverse position shift of the substrate. Such a Fabry-Perot filter is designed and fabricated and used as an output coupler of a c-cut Nd:YVO laser experimentally in this paper to obtain a 1062 and 1083 nm dual-wavelength laser. The peak transmission wavelengths are gradually shifted from 1040.

Tailoring the plasmonic whispering gallery modes of a metal-coated resonator for potential application as a refractometric sensor.

Plasmonic whispering gallery (WG) modes confined in metal-coated resonators are theoretically investigated by electromagnetic analyses. The resonance can be tuned from internal surface plasmonic WG modes to the hybrid state of the plasmonic mode by an introduced isolation layer. As the coated metal is reduced in size, the optical resonance is shifted out by the mode coupling of the internal and external surface plasmonic WG modes.

Super-long photonic nanojet generated from liquid-filled hollow microcylinder.

Photonic nanojet (PNJ) from liquid-filled hollow microcylinder (LFHM) under a liquid immersion condition is numerically investigated based on the finite element method and physically analyzed with ray optics. Simulation and analysis results show that, by simultaneously introducing the immersed liquid and filled liquid, the propagation beam is greatly flattened, and super-long PNJs with decay length more than 100 times the illumination wavelengths are obtained in the outer near-field region of the LFHM. With the variation of the refractive index contrast between the filled and immersed-liquids, the properties of the PNJs, such as the focal distance, decay length, full width at half-maximum, and maximum light intensity can be flexibly tuned.