作者机构：
[An, Feng Hui] Jiujiang Univ, Jiangxi Prov Engn Res Ctr Mat Surface Remfg, Jiujiang 332005, Jiangxi, Peoples R China.;[Yuan, Yu Zheng; He, Meng Dong] Cent South Univ Forestry & Technol, Inst Math & Phys, Changsha 410004, Peoples R China.;[Liu, Jian Qiang] Jiujiang Univ, Coll Sci, Jiujiang 332005, Jiangxi, Peoples R China.;[Zhang, Bo] Jiangxi Univ Sci & Technol, Energy Mat Comp Ctr, Sch Energy & Mech Engn, Nanchang, Peoples R China.
通讯机构：
[Liu, Jian Qiang] C;College of Science, Jiujiang University Jiujiang Jiangxi 332005 China
摘要：
Tungsten oxide is regarded as the most promising electrochromic material owing to its continuously tunable optical properties, low cost, and high coloration efficiency. Further improving its optical modulation, switching speed, and coloration efficiency is important to electrochromic smart windows and related devices. Here, we demonstrate an enhanced electrochromic film composed of a WO(3) nanosheet and ITO nanoparticles developed by an all-solution technology. The WO(3) nanosheet is fabricated by an acid-assisted hydrothermal process with high product efficiency. The introduction of an ITO into the WO(3) nanosheets significantly improved the electrochemical activity and the conductivity of the composite film. Compared with a reported electrochromic film without ITO doping, our synthesized composite WO(3) film exhibited optical modulation up to 88% and a high coloration efficiency of 154.16 cm(2) C(-1). Particularly, our electrochromic film was based on the dispersant solution and spin-coating technology, which may also be realized with nano-spray coating for large scale applications. The results offer an effective way to develop large-area electrochromic film and devices.
摘要：
The non-linear responses of optical materials offer useful mechanisms for optical switching, novel optical sources, and harmonic frequency conversion. However, the non-linear response of traditional materials is usually extremely weak and requires high input power for excitation. In this study, we theoretically propose a scheme for enhancing the third harmonic generation (THG) efficiency and output power of layered graphene disks array by introducing a plasmonic antibonding state with enhanced oscillation strength due to plasmonic coupling. We verify that, the THG efficiency of a double-layer stacked graphene/SiO2 disk structure under relatively low input intensity can be significantly enhanced more than one order of magnitude with appropriate design, as compared with monolayer patterned graphene nanostructure. We also demonstrate that the THG efficiency can be further improved by optimizing the geometry parameters such as spacer distance and Fermi energy. Our results offer an effective mechanism for significantly improving THG efficiency in the mid-infrared and terahertz ranges, thereby paving the way for new frequency converters and modulators in optical communication and signal processing.
摘要：
We propose a scheme of a sensitive biosensor based on optical bistability (OB) in a biological semiconductor quantum dot (SQD)-DNA coupled nanohybrid. By plotting bistability phase diagrams within the system's parameter space, we show that the bistable effect can be switched on or off by only tuning the pumping intensity or the detuning of the pump field from the exciton resonance. Simultaneously, we reveal that the bistability only exists in the strong SQD-DNA coupling regime. Specifically, we derive the matching relation between the excitation conditions and the coupling strength when the bistability just appears. Moreover, we demonstrate that the OB is highly sensitive to the SQD-DNA coupling strength which is strongly correlated to the length of DNA molecules and DNA concentration. This investigation may be useful for opening a new way to build optical switches and providing a novel and convenient platform to detect DNA molecules.
摘要：
<![CDATA[<ce:abstract xmlns:ce="" xmlns="" class="author" view="all" id="d1e513"><ce:section-title id="d1e514">Abstract</ce:section-title><ce:abstract-sec view="all" id="d1e516"><ce:simple-para view="all" id="d1e517">In this paper, we demonstrate the effect of polarization conversion in a plasmonic metasurface structure, in which each unit cell consists of a metal bar and four metal split-ring resonators (SRRs). Such effect is attributed to the fact that the dark plasmon mode of SRRs (bar), which radiates cross-polarized component, is induced by the bright plasmon mode of bar (SRRs) due to the electromagnetic near-field coupling between bar and SRRs. We find that there are two ways to achieve a large cross-polarized component in our proposed metasurface structure. The first way is realized when the dark plasmon mode of bar (SRRs) is in resonance, while at this time the bright plasmon mode of SRRs (bar) is not at resonant state. The second way is realized when the bright plasmon mode of SRRs (bar) is resonantly excited, while the dark plasmon mode of bar (SRRs) is at nonresonant state. It is also found that the linearly polarized light can be rotated by 56.5<mml:math xmlns:mml="" id="mml22" display="inline" overflow="scroll" altimg="si22.gif"><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:math>after propagation through the metasurface structure. Furthermore, our proposed metasurface structure exhibits an asymmetric transmission for circularly polarized light. Our findings take a further step in developing integrated metasurface-based photonics devices for polarization manipulation and modulation.</ce:simple-para></ce:abstract-sec></ce:abstract><ce:abstract xmlns:ce="" xmlns="" class="author-highlights" view="all" id="d1e537"><ce:section-title id="d1e538">Highlights</ce:section-title><ce:abstract-sec view="all" id="d1e540"><ce:simple-para view="all" id="d1e541"><ce:list id="d1e543"><ce:list-item id="d1e544"><ce:label>•</ce:label><ce:para view="all" id="p1">We demonstrated the effects of polarization conversion and asymmetric transmission in plasmonic metasurfaces.</ce:para></ce:list-item><ce:list-item id="d1e551"><ce:label>•</ce:label><ce:para view="all" id="p2">The dark plasmon mode is induced by a bright plasmon mode due to electromagnetic near field coupling.</ce:para></ce:list-item><ce:list-item id="d1e558"><ce:label>•</ce:label><ce:para view="all" id="p3">There are two ways to achieve a large cross-polarized component.</ce:para></ce:list-item></ce:list></ce:simple-para></ce:abstract-sec></ce:abstract>]]>
摘要：
We designed and numerically investigated a mechanism to enhance the polarization rotation when THz radiation passes through an array of multilayered graphene/insulator disks placed in a static magnetic field. The observed giant Faraday rotation is due to plasmonic coupling in the disks leading to the enhanced dipole oscillation strength of plasmonic antibonding states. With additional electromagnetic coupling between the disks in the array, the Faraday rotation angles nearly 30° are achieved in a relatively small external magnetic field of around 1 T. The operation wavelength can be tuned within the THz spectral range by controlling the Fermi level of graphene, number of graphene layers, and disk size and period. The proposed mechanism opens up a way to design the ultrathin magneto-optical nanophotonic devices and polarization rotators with high transmittance in the mid-infrared range.
摘要：
Based on the interplay between propagating surface plasmon polaritons (PSPs) in graphene ribbon and double layer sheets structure, we theoretically demonstrate a tunable strong coupling mechanism significantly different from reported conventional noble metal nanostructures. The strong electromagnetic coupling between the low order antisymmetric and high order symmetric PSPs modes occurs due to the intersections of dispersion curves, which leads to a modification of plasmonic dispersion and multiple significant anti-crossing regions. Of particular, this strong coupling is controllable through external gate voltage of graphene sheets or ribbon. The results offer an effective regime to dynamically tune the interaction of graphene PSPs, which may find applications in the field of nanophotonic devices in the mid-infrared range.
摘要：
We report the tunable enhanced transmission of light through a hybrid metal-graphene structure, in which a graphene ribbon array is situated over a metallic grating. The graphene ribbon is employed to make the graphene-insulator-metal waveguide of finite length as a Fabry-Perot (F-P) cavity. When the slit of metallic grating is opened at the position with a maximal magnetic field in F-P resonant cavity, the transmission of light through metallic grating is greatly enhanced since the strongly localized magnetic field is effectively coupled to the slit. The transmission spectrum and the enhancement factor can be adjusted by changing geometrical parameters including the width and the length of slit, the width of graphene ribbon and the period of metallic grating. The transmission peaks exhibit a broad tuning range with a small change in the Fermi energy level of graphene. Moreover, the enhancement factor of transmission peak can be manipulated by the Fermi energy level and the carrier mobility of graphene, and an enhancement factor of 154 is obtained. The findings expand our understanding of hybrid metal-graphene plasmons and have potential applications in building active plasmonic devices. (C) 2016 Elsevier B.V. All rights reserved.
摘要：
We present a computational study of the plasmon resonances in a periodic square coaxial hole array in a graphene sheet, which consists of a square hole array and a square strip array. According to charge oscillation picture, we find that a new plasmon mode, which locates on the edges of square hole along the polarization direction of incident light, emerges in our proposed structure. Two hybridized plasmon resonance modes (i.e., symmetric and asymmetric plasmon resonance modes) are formed due to two different manners of coupling between the new plasmon mode of square hole and the plasmon mode of square strip. The two plasmon resonance modes can be tuned over a wide wavelength range by a small change in the chemical potential of graphene. Furthermore, the two plasmon resonances can also be controlled by changing L
x
and L
y
(which are the strip offsets from the hole center perpendicular and parallel to the polarization direction of incident light, respectively), originating from the change in the strength of electromagnetic coupling between square hole and square strip. Our study gives an insight into the physical mechanism of plasmon resonances in square graphene coaxial hole array, and our findings will be useful for designing graphene-based plasmonic devices and metamaterials.
期刊：
International Journal of Modern Physics B,2016年30(16):1650088 ISSN：0217-9792
通讯作者：
He, Meng-Dong
作者机构：
[Peng, Yu-Xiang; Li, Ze-Jun; Wang, Kai-Jun; Liu, Ling-Hong; Wang, Lei; Wang, Xin-Jun; He, Meng-Dong; Li, Jian-Bo] Cent South Univ Forestry & Technol, Inst Math & Phys, Changsha 410004, Hunan, Peoples R China.;[Xu, Liang] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[He, Meng-Dong] C;Cent South Univ Forestry & Technol, Inst Math & Phys, Changsha 410004, Hunan, Peoples R China.
关键词：
Surface plasmon polaritons;plasmon resonance energy transfer;metallic grating;reduced cytochrome c molecule
摘要：
We investigate the transmission characteristics of a one-dimensional metallic grating covered by a reduced cytochrome (Cyt) c molecule layer by using the finite-difference time-domain (FDTD) method. It is found that the introduction of reduced Cyt c molecule layer leads to a transmission dip due to the plasmon resonance energy transfer (PRET) from metallic grating to Cyt c molecules. The transmission dip depth can be controlled by the period of metallic grating, the width and length of slit, and the Cyt c molecule layer number, while the transmission dip wavelength is unchanged with these parameters. The findings expand our understanding of the PRET phenomenon and have potential applications in molecule identification and detection.
通讯机构：
[He, Meng-Dong] C;Cent South Univ Forestry & Technol, Inst Math & Phys, Changsha 410004, Hunan, Peoples R China.
关键词：
Localized surface plasmon resonance;Plasmon resonance energy transfer;Metallic nanoparticle array;Reduced cytochrome c molecule
摘要：
We investigate the optical properties of a metallic nanoparticle array covered by a reduced cytochrome (Cyt) c molecule layer by using the finite-difference time-domain method. As the wavelength of the surface plasmon resonance of metallic nanoparticle array matches with that of the absorption peak of reduced Cyt c molecules, a pronounced spectral dip forms in extinction spectrum due to the plasmon resonance energy transfer from metallic nanoparticles to Cyt c molecules. The depth of extinction dip can be controlled by the length and width of metallic nanoparticle, the grating constant, and the Cyt c molecule layer number, though the position of extinction dip is unchanged with these parameters. The findings may find applications in molecule identification and detection.
