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Tunable Mid-Infrared Graphene Plasmonic Cross-Shaped Resonator for Demultiplexing Application
摘要： In this study, a tunable graphene plasmonic ?lter and a two-channel demultiplexer are proposed, simulated, and analyzed in the mid-infrared (MIR) region. We discuss the optical transmission spectra of the proposed cross-shaped resonator and the two-channel demultiplexer. The transmission spectra of the proposed MIR resonator are tunable by change of its dimensional parameters and the Fermi energy of the graphene. Our proposed structures have a single mode in the wavelength range of 5–12 μm. The minimum full width at half maximum (FWHM) and the maximum transmission ratio of the proposed resonator respectively reached 220 nm and 55%. Simulations are performed by use of three-dimensional ?nite-di?erence time-domain (3D-FDTD) method. Coupled mode theory (CMT) is used to investigate the structure theoretically. The numerical and the theoretical results are in good agreement. The performance of the proposed two-channel demultiplexer is investigated based on its crosstalk. The minimum value of crosstalk reaches ?48.30 dB. Our proposed structures are capable of providing sub-wavelength con?nement of light waves, useful in applications in MIR region.
关键词： resonator,plasmonics,graphene,Fermi energy,demultiplexer
更新于2025-09-23 15:19:57
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Arbitrary control of the diffusion potential between a plasmonic metal and a semiconductor by an angstrom-thick interface dipole layer
摘要： Localized surface plasmon resonances (LSPRs) are gaining considerable attention due to the unique far-field and near-field optical properties and applications. Additionally, the Fermi energy, which is the chemical potential, of plasmonic nanoparticles is one of the key properties to control hot-electron and -hole transfer at the interface between plasmonic nanoparticles and a semiconductor. In this article, we tried to control the diffusion potential of the plasmonic system by manipulating the interface dipole. We fabricated solid-state photoelectric conversion devices in which gold nanoparticles (Au-NPs) are located between strontium titanate (SrTiO3) as an electron transfer material and nickel oxide (NiO) as a hole transport material. Lanthanum aluminate as an interface dipole layer was deposited on the atomic layer scale at the three-phase interface of Au-NPs, SrTiO3, and NiO, and the effect was investigated by photoelectric measurements. Importantly, the diffusion potential between the plasmonic metal and a semiconductor can be arbitrarily controlled by the averaged thickness and direction of the interface dipole layer. The insertion of an only one unit cell (uc) interface dipole layer, whose thickness was less than 0.5 nm, dramatically controlled the diffusion potential formed between the plasmonic nanoparticles and surrounding media. This is a new methodology to control the plasmonic potential without applying external stimuli, such as an applied potential or photoirradiation, and without changing the base materials. In particular, it is very beneficial for plasmonic devices in that the interface dipole has the ability not only to decrease but also to increase the open-circuit voltage on the order of several hundreds of millivolts.
关键词： interface dipole,Fermi energy,strontium titanate,nickel oxide,hole transfer,hot-electron,lanthanum aluminate,gold nanoparticles,photoelectric conversion,Localized surface plasmon resonances
更新于2025-09-23 15:19:57
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Single-Walled boron nitride nanotubes interaction with nickel, titanium, palladium, and gold metal atoms- A first-principles study
摘要： Ab initio calculations based on density functional theory was carried out to study the electronic properties of (3,3), (4,2), (5,2) and (6,0) boron nitride nanotubes when interacting with nickel, titanium, palladium and gold metal atoms. These interactions occurred via adsorption, intercalation, nitrogen substitutional doping and boron substitutional doping. The wide band gaps intrinsic to the pristine boron nitride nanotubes were successfully tuned upon interaction with the metal atoms irrespective of the type of interactions. However, for most of the interactions that occurred via intercalation and nitrogen substitutional doping, the boron nitride nanotube was found to possess semi-metallic properties. More states were added in the density of states upon interaction in which the d orbital of the transition metal atoms was found to be the major contributor to the increase in density of states.
关键词： Transition metals,Fermi energy,Density functional theory,Band gap,Boron nitride nanotubes
更新于2025-09-19 17:13:59
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Redefinition the quasi-Fermi energy levels separation of electrons and holes inside and outside quantum wells of GaN based multi-quantum-well semiconductor laser diodes
摘要： Both accurate experiments and a self-consistent theoretical simulation using the near-ABC or ab initio method have uncovered the anomalous changes in the junction voltage (Vj ) of GaN-based lasers (Li et al 2013 Appl. Phys. Lett. 102 123501, Feng et al 2018 J. Phys. D: Appl. Phys. 51 095102 and Feng et al Appl. Phys. B 124 39). Here, further accurate emission spectral characteristics and band-gap simulation of a GaN based laser diodes (LDs) confirmed that previous researchers may have confused the junction voltage (Vj ) and the separation between the two Fermi levels of electrons and holes in the active region divided by the electronic charge (ΔEf /e). For the multiple-quantum wells (MQWs), there are obvious differences between them. For an ideal GaN-based LDs, despite the increase in junction voltage, physical quantities including the separation between the two Fermi levels of electrons and holes in the MQW region, and the optical net gain remain unchanged beyond the threshold region after an unpredictable sharp increase in the threshold region.
关键词： multi-quantum-well (MQW),steady state,junction voltage,quasi-Fermi energy levels separation,GaN based laser diodes (LD)
更新于2025-09-19 17:13:59
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Mathematical Modelling of Electrically Controlled Filters of Microwave, subTHz and THza??bands on the Base of Grapheneand-Dielectric Multilayer Structure
摘要： Report is devoted to investigations of graphene meta–surfaces for the transmission of radiation induced by plasmons in subTHz and THz ranges, cell of which consists of structures based on graphene ring and graphene nano–tape. It create regimes of radiation transmission – transparency windows induced by electric dipole resonances. Resonant frequency of transparency window can be dynamically tuned in wide band of subTHz and THz bands by changing the chemical potential (Fermi energy) of graphene by applying external electric field (gating) instead of re–fabricating of structures. Questions of possibilities of electronic controlled filters creating of subTHz and THz bands grounded on different configurations of graphene meta–surfaces are discussed; their characteristics and frequency dependencies are investigated. Mathematical modelling and electrodynamic calculation of the filters characteristics of subTHz and THz bands grounded on multilayer structures of “graphene–dielectric” type are carried out. From results of mathematical modelling it follows that periodic layered microstructures “graphene–dielectric” type can be used for creation of subTHz and THz bands broadband filters of planar construction, controlling by electric field and fast tuning at small changes in Fermi energy level of graphene.
关键词： multilayer structures,filters,subTHz,plasmonic,chemical potential,electric field,graphene,meta-surfaces,electric dipole resonances,THz,Fermi energy
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Ultra-Deep Sub-Wavelength Mode Confinement in Graphene Waveguides
摘要： In this paper, a nano-structured device is designed using two adjacent graphene-based waveguides which is capable of con?ning an incident light-wave at the deep nano-scale. The Fermi energy of graphene in both waveguides are tuned by electrostatic gating, providing an active control on the working frequency of the device.
关键词： Fermi energy tuning,graphene waveguides,surface plasmon polaritons,ultra-deep sub-wavelength mode con?nement
更新于2025-09-12 10:27:22
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Ag ion implanted TiO2 photoanodes for fabrication of highly efficient and economical plasmonic Dye Sensitized Solar Cells
摘要： Materials with tunable optical and photoelectric properties are prerequisite for the development of highly stable, economical and efficient dye sensitized solar cells (DSSCs). In this direction, improved plasmonic DSSCs with comparatively higher light harvesting ability and reduced recombination of photo-generated charge carriers have been fabricated using low energy (120 KeV) Ag ion implanted TiO2 photoanodes at variable fluence. Herein, the origin of improved photovoltaic performance of Ag implanted DSSCs against conventional DSSC has been explained using UV-visible, photoluminescence and kelvin probe measurements. Further, the efficient interfacial charge transportation within Ag implanted DSSCs has been demonstrated through EIS measurements.
关键词： Fermi energy equilibration,Ion Implantation,Localized Surface Plasmon Resonance (LSPR)
更新于2025-09-12 10:27:22
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Geometry-diversified Coulomb excitations in trilayer AAB stacking graphene
摘要： The lower-symmetry trilayer AAB-stacked graphene exhibits rich electronic properties and diverse Coulomb excitations. Three pairs of unusual valence and conduction bands create nine available interband excitations for the undoped case, in which the imaginary (real) part of the polarizability shows one-dimensional square root asymmetric peaks and two-dimensional shoulder structures (pairs of antisymmetric peaks and logarithm-type symmetric peaks). The low-frequency acoustic plasmon, being revealed as a prominent peak in the energy-loss spectrum, can survive in a narrow-gap system with the large density of states from the valence band. This type of plasmon mode is similar to that in a narrow-gap carbon nanotube. However, the decisive mechanism governing this plasmon is the intraband conduction state excitations. Its frequency, intensity and critical momentum exhibit a nonmonotonic dependence on the Fermi energy. The well-de?ned electron-hole excitation boundaries and the higher frequency optical plasmons are transformed by varying the Fermi energy. Many substantial differences between the electronic properties of AAB and other trilayer graphene stackings are discussed.
关键词： Coulomb excitations,Fermi energy,electronic properties,plasmon modes,trilayer AAB-stacked graphene
更新于2025-09-09 09:28:46