Strong and weak polarization-dependent interactions in connected and disconnected plasmonic nanostructures

We explore numerically and experimentally the formation of hybridized modes between a bright mode displayed by a gold nanodisc and either dark or bright modes of a nanorod - both...

Demonstration of toroidal metasurfaces through near-field coupling of bright mode resonators

Bright mode resonances are not well-acknowledged for inducing mode hybridizations. However, we demonstrate multiple bright resonators coupled through electromagnetic fields can induce resonance mode hybridizations. Although one of the hybridized modes shows parallel magnetic moments but the other mode demonstrates anti-parallel magnetic moments leading to magnetic toroidal resonances. Normally excitation of toroidal modes demands complex structures and/or bright-dark mode interactions. However, in this work, we employ solely bright resonators to excite toroidal modes. Unlike bright-dark mode coupling, exclusive bright mode resonance coupling enables larger free space energy merging into the metasystem leading to stronger energy confinement in the metasurface array.

Plasmons Coupling and Anti-Crossing of Nanometal Asymmetric Dimer

In this paper, by defining a new physical quantity called as the frequency offset in the harmonic oscillator model and combining with the established plasmon coupling model, we successfully explain the anti-crossing property caused by plasmon coupling of dimer composed of a silver nanoring and a silver nanorod. In the plasmons coupling model, we reasonably reveal that the physical mechanism of the coupling between bright mode and dark mode of the plasmons is mainly represented by the coulomb potential and the electrostatic potential. With this model, we explain also the asymmetric feature the variation of frequency offset and coupling coefficient with coupling distance.

Bio-inspired Artificial Helical Chromatophore for Stealth Mode

<p>Stealth technology has been very usefully applied in the military fields and is now becoming more prominent as a strategic technology. In nature, the firefly squid can protect itself from enemies using camouflage as a stealth mode. On the other hand, it is able to send fluorescent signals to attract prey by switching into a bright mode. Despite the development of many existing biomimetic materials, there are significant constraints related to their color-changeable velocity and mobility. Herein, we have developed a bio-inspired artificial thermochromic material system, which can reversibly switch between stealth and bright modes and thus provide a means to adapting to one’s environment analogous to the strategy applied by firefly squids. Through vertical contraction, a helically coiled yarn artificial muscle, selectively coated by Rhodamine B and TiO₂, can switch between fluorescent and stealth modes with a maximum speed of 0.31 cm/s. Upon external thermal impulse, artificial thermochromic muscle can spin up to 309° and achieve a negative strain of 84.6%. In addition, this research demonstrates thermochromic effects even in underwater aqueous conditions, showing applicability toward underwater robotics. With the cost-effectiveness of the demonstrated system, the developed artificial thermochromic muscles can be implemented into a variety of applications, such as colorimetric sensors and aqueous color-changeable soft robotics.</p>

Bio-inspired Artificial Helical Chromatophore for Stealth Mode

<p>Stealth technology has been very usefully applied in the military fields and is now becoming more prominent as a strategic technology. In nature, the firefly squid can protect itself from enemies using camouflage as a stealth mode. On the other hand, it is able to send fluorescent signals to attract prey by switching into a bright mode. Despite the development of many existing biomimetic materials, there are significant constraints related to their color-changeable velocity and mobility. Herein, we have developed a bio-inspired artificial thermochromic material system, which can reversibly switch between stealth and bright modes and thus provide a means to adapting to one’s environment analogous to the strategy applied by firefly squids. Through vertical contraction, a helically coiled yarn artificial muscle, selectively coated by Rhodamine B and TiO₂, can switch between fluorescent and stealth modes with a maximum speed of 0.31 cm/s. Upon external thermal impulse, artificial thermochromic muscle can spin up to 309° and achieve a negative strain of 84.6%. In addition, this research demonstrates thermochromic effects even in underwater aqueous conditions, showing applicability toward underwater robotics. With the cost-effectiveness of the demonstrated system, the developed artificial thermochromic muscles can be implemented into a variety of applications, such as colorimetric sensors and aqueous color-changeable soft robotics.</p>

Tunable Plasmon-Induced Transparency through Bright Mode Resonator in a Metal–Graphene Terahertz Metamaterial

The combination of graphene and metamaterials is the ideal route to achieve active control of the electromagnetic wave in the terahertz (THz) regime. Here, the tunable plasmon-induced transparency (PIT) metamaterial, integrating metal resonators with tunable graphene, is numerically investigated at THz frequencies. By varying the Fermi energy of graphene, the reconfigurable coupling condition is actively modulated and continuous manipulation of the metamaterial resonance intensity is achieved. In this device structure, monolayer graphene operates as a tunable conductive film which yields actively controlled PIT behavior and the accompanied group delay. This device concept provides theoretical guidance to design compact terahertz modulation devices.

Broadband Filter and Adjustable Extinction Ratio Modulator Based on Metal-Graphene Hybrid Metamaterials

A novel multifunctional device based on a hybrid metal–graphene Electromagnetically induced transparency (EIT) metamaterial at the terahertz band is proposed. It is composed of a parallel cut wire pair (PCWP) that serves as a dark mode resonator, a vertical cut wire pair (VCWP) that serves as a bright mode resonator and a graphene ribbon that serves as a modulator. An ultra-broadband transmission window with 1.23 THz bandwidth can be obtained. The spectral extinction ratio can be tuned from 26% to 98% by changing the Fermi level of the graphene. Compared with previous work, our work has superior performance in the adjustable bandwidth of the transmission window without changing the structure of the dark and bright mode resonators, and has a high extinction ratio and dynamic adjustability. Besides, we present the specific application of the device in filters and optical modules. Therefore, we believe that such a metamaterial structure provides a new way to actively control EIT-like, which has promising applications in broadband optical filters and photoelectric intensity modulators in terahertz communications.