Houbo Chen

Optimization of the Fano Resonance Lineshape Based on Graphene Plasmonic Hexamer in Mid-Infrared Frequencies

In this article, the lineshape of Fano-like resonance of graphene plasmonic oligomers is investigated as a function of the parameters of the nanostructures, such as disk size, chemical potential and electron momentum relaxation time in mid-infrared frequencies. Also, the mechanism of the optimization is discussed. Furthermore, the environmental index sensing effect of the proposed structure is revealed, and a figure of merit of 25.58 is achieved with the optimized graphene oligomer. The proposed nanostructure could find applications in the fields of chemical or biochemical sensing.

Topologically protected edge states in graphene plasmonic crystals

A two-dimensional graphene plasmonic crystal composed of periodically arranged graphene nanodisks is proposed. We show that the band topology effect due to inversion symmetry broken in the proposed plasmonic crystals is obtained by tuning the chemical potential of graphene nanodisks. Utilizing this kind of plasmonic crystal, we constructed N-shaped channels and realized topologically edged transmission within the band gap. Furthermore, topologically protected exterior boundary propagation, which is immune to backscattering, was also achieved by modifying the chemical potential of graphene nanodisks. The proposed graphene plasmonic crystals with ultracompact size are subject only to intrinsic material loss, which may find potential applications in the fields of topological plasmonics and high density nanophotonic integrated systems.

Investigation of plasmonic whispering gallery modes of graphene equilateral triangle nanocavities

In this paper, a graphene-based equilateral triangle nanocavity is proposed and numerically investigated. The relationship between the mode characteristics and the nanocavity parameters, such as the geometry of nanocavity and the chemical potential of graphene, is systematically explored. A high-order plasmonic WGM (whispering gallery mode) with a high quality factor of 147.93 is obtained in our nanocavity with a wavelength of around 1.415 µm in free space, with a corresponding Purcell factor as high as 7.067 × 108. The proposed plasmonic WGM nanocavity could be a key component of the high density plasmonic integrated circuits due to its ultra-compactness and performances.

Investigation of the Band Structure of Graphene-Based Plasmonic Photonic Crystals

In this paper, one-dimensional (1D) and two-dimensional (2D) graphene-based plasmonic photonic crystals (PhCs) are proposed. The band structures and density of states (DOS) have been numerically investigated. Photonic band gaps (PBGs) are found in both 1D and 2D PhCs. Meanwhile, graphene-based plasmonic PhC nanocavity with resonant frequency around 175 THz, is realized by introducing point defect, where the chemical potential is from 0.085 to 0.25 eV, in a 2D PhC. Also, the bending wvaguide and the beam splitter are realized by introducing the line defect into the 2D PhC.

Ultra-compact tunable graphene-based plasmonic multimode interference power splitter in mid infrared frequencies

In this paper, we propose graphene-based plasmonic multimode interference power splitters with ultra-compact size working in mid infrared range. Further, the arbitrary-ratio 1×2 power splitter with a size of 140 nm×232 nm, where the splitting ratio can be tuned continuously from 1:1 to 100:0, is numerically demonstrated. Meanwhile, the graphene-based arbitrary-ratio 1×2 power splitters with different frequencies and chemical potentials are also investigated. The proposed multimode interference structure with a deep nanoscale footprint might be a fundamental component of the future high density integrated plasmonic circuit or on-chip plasmonic interconnect techniques.

Plasmonic mode analysis of deep subwavelength graphene nanoribbon waveguides

Abstract. Deep subwavelength plasmonic graphene nanoribbon waveguides for telecommunication frequencies are proposed. The mode properties of graphene nanoribbon waveguides with varied chemical potential are numerically investigated in terms of the effective indices and the propagation length of the plasmonic modes. A refractive index as high as 4980 is obtained on the plasmonic mode along the nanoribbon waveguide with a width of 3 nm at a frequency of 190 THz, and the normalized mode area on the scale of 10−8(1/λ0)2. An embedded graphene nanoribbon waveguide was also proposed and it is that the optical characteristic can be tuned by adjusting the chemical potential of graphene. The proposed structure can be a fundamental component of the future integrated plasmonic circuit system.

Investigation of beam splitter in a zero-refractive-index photonic crystal at the frequency of Dirac-like point

The Dirac-like cone dispersion of the photonic crystal induced by the three-fold accidental degeneracy at the Brillouin center is calculated in this paper. Such photonic crystals can be mapped to zero-refractive-index materials at the vicinity of the Dirac-like point frequency, and utilized to construct beam splitter of high transmission efficiency. The splitting ratio is studied as a function of the position of the input/output waveguides. Furthermore, variant beam splitters with asymmetric structures, bulk defects, and some certain bending angles are numerically simulated. Finally, we show that 1 × 2 to 1 × N beam splitting can be realized with high transmission efficiency in such a zero-refractive-index photonic crystal at the frequency of Dirac-like point. The proposed structure could be a fundamental component of the high density photonic integrated circuit technique.