Plasmonic properties of folded graphene nanodisks

Zhang, Rui; Wang, Shengchuan; You, Bin; Han, Kui; Shen, Xiaopeng

doi:10.1088/2040-8986/abceaa

Cited by 9 publications

(7 citation statements)

References 48 publications

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“…As θ increases from 10 • to 30 • , a large blueshift is observed for the VM, while there is a tiny redshift for the PM. Interestingly, the frequency change can be well described by a simple exponential formula [38]. The feature of PM, and that of DM (dark yellow curve, independent of θ), ensures the occurrence of a PIT window for all θ (see figure 3(b)), which is the lower frequency one (point e at figure 2(c)).…”

Section: Resultsmentioning

confidence: 88%

“…Symmetry breaking is introduced by operating one of the two nanodisks via structural folding, a new freedom to manipulate graphene resonators in the vertical direction, rather than in the horizontal plane. In a folded nanodisk, the two fundamental dipole resonances are no longer degenerate, with one parallel (parallel mode, PM) and the other perpendicular (vertical mode, VM) to the folding axis [38], and their Q factors increase dramatically as compared to those (bright dipole modes, DMs) in the planar nanodisk. PIT emerges from the coupling of PM/VM to DM, and can be manipulated by changing the folding angle, Fermi level, and separation.…”

Section: Introductionmentioning

confidence: 99%

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Folding-assisted plasmonically induced transparency in coupled graphene nanodisks

Wang

Zhang

2022

J. Opt.

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Plasmonically induced transparency (PIT), a classical analogue of electromagnetically induced transparency in quantum systems, could offer an efficient way to engineer light-matter interaction and thus achieve particular manipulation of light. To realize PIT, the crucial point is the design of two strongly coupled modes, with one bright and the other dark. The common practice often takes dipole resonance as the bright mode, while higher order resonance as the dark one. We present here an alternative scheme to realize PIT in coupled graphene nanodisks through mechanical folding, where only fundamental dipole resonances are involved, and the dark mode is derived from two nondegenerate dipole resonances in folded nanodisk. Two parameters (folding angle and rotating angle ) arising from folding can be utilized to tune PIT. They determine two different PIT windows separately. By varying either one of them, single-window PIT can be switched to double-window PIT, and vice versa. Besides the mechanical operations, the proposed PIT can also be actively tuned by electrostatic gating. To understand the mechanism properly, a theoretical model of two coupled harmonic oscillators is presented, from which the predictions show good agreement with simulations.

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Section: Resultsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Folding-assisted plasmonically induced transparency in coupled graphene nanodisks

Wang

Zhang

2022

J. Opt.

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“…As usual, the optical response of graphene is characterized by the macroscopic surface conductivity σ (ω), which can be rigorously derived within the framework of random phase approximation [45,46]. In the absence of a perpendicular magnetic field, σ (ω) can be readily written down as [47]…”

Section: Resultsmentioning

confidence: 99%

Symmetry-protected bound states in the continuum in graphene nanoribbons

Wang¹,

You²

2022

J. Opt.

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Bound states in the continuum (BICs) have emerged as a significant design principle for producing systems with high-quality (Q) factor states to enhance light-matter interactions. As a particular case, symmetry-protected BICs are flexible to be designed, commonly by utilizing two identical lossless dielectric elements. Herein, different from previous studies, we propose symmetry-protected BICs in a plasmonic structure of two contacting graphene nanoribbons (GNRs), in which two GNRs are not identical and lossy. We show that BICs are achieved when two GNRs are perpendicular to each other, and as the vertical GNR deviates from the vertical direction (inversion symmetry breaking), it will evolve into quasi-BICs, with a new resonance dip appearing in the transmission spectrum. The spectrum curve can be well described by the coupled-mode theory, from which the variation of two fundamental states is clearly seen. Since in the presence of internal loss, the Q-factor of quasi-BICs does not follow the linear formula that is generally valid for symmetry-protected BICs. Alternatively, an extended formula is derived, which predicts exactly the behavior of the Q-factor of quasi-BICs. Besides BICs, the structure can also support plasmonically induced transparency (PIT) like effects, through rotating the vertical GNR to a particular angle. Therefore, a mechanically tunable switch, from BIC to PIT, is achieved here. Our work demonstrates an alternative scheme for BICs, and a new degree of freedom for tuning plasmonic coupling related effects.

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“…[5][6][7] In contrast to plasmons in three-dimensional (3D) noble metals, they exhibit significant advantages in field confinement and propagation, [8][9][10] and more remarkably, their resonance frequencies lying in the terahertz (THz) and/or infrared region can be tuned dynamically through electrostatic gating, 11,12 static magnetic field, [13][14][15][16] and mechanical folding. [17][18][19] By placing a metal reflector, sharing an identical idea of metal-insulator-metal (MIM) designs, graphene plasmons can achieve exact 100% OA at plasmonic resonance frequencies, [20][21][22] thus achieving narrowband complete OA. However, because of the discrete feature of these frequencies, it is quite challenging to engineer broadband complete OA in plasmonic systems, where a basic trade-off occurs between absorption efficiency and bandwidth.…”

Section: Introductionmentioning

confidence: 99%