Tunable Toroidal Response in a Reconfigurable Terahertz Metamaterial

Chen, Chunxu; Kaj, Kelson; Huang, Yi; Zhao, Xiaoguang; Averitt, Richard D.; Zhang, Xin

doi:10.1002/adom.202101215

Cited by 13 publications

(6 citation statements)

References 57 publications

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“…As a result, the actuation of cantilevers can not only shift the resonance frequency from 0.74 THz to 1.34 THz but also change the phase span of the mode from a full 2π range (OFF state) to π range (ON state) as shown in Figure 4(c). Meanwhile, toroidal responses could also be probed with the spatial deformation of MEMS cantilevers by utilizing four split-ring resonators (SRRs, Figure 4(d)) arranged in one supercell [67]. In the planar configuration, toroidal responses (head-to-tail magnetic dipoles) were enhanced by the neighboring opposite orientated SRRs, but the enhancement of the toroidal component is limited in such a planar configuration.…”

Section: Intrabandmentioning

confidence: 99%

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Terahertz Metamaterials for Free-Space and on-Chip Applications: From Active Metadevices to Topological Photonic Crystals

Xing

Fan

et al. 2022

Adv Devices Instrum

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Terahertz (THz) waves have exhibited promising applications in imaging, sensing, and communications, especially for the next-generation wireless communications due to the large bandwidth and abundant spectral resources. Modulators and waveguides to manipulate THz waves are becoming key components to develop the relevant technologies where metamaterials have exhibited extraordinary performance to control free-space and on-chip propagation, respectively. In this review, we will give a brief overview of the current progress in active metadevices and topological photonic crystals, for applications of terahertz free-space modulators and on-chip waveguides. In the first part, the most recent research progress of active terahertz metadevices will be discussed by combining metamaterials with various active media. In the second part, fundamentals of photonic topological insulations will be introduced where the topological photonic crystals are an emerging research area that would boost the development of on-chip terahertz communications. It is envisioned that the combination of them would find great potential in more advanced terahertz applications, such as reconfigurable topological waveguides and topologically-protected metadevices.

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Section: Intrabandmentioning

confidence: 99%

“…(c) Active phase transition via loss engineering in MEMS metamaterials[66]. (d) Tunable toroidal response in a reconfigurable terahertz MEMS metadevice[67]. (e) Topology-changing metamaterials enabled by closable nanotrenches for broadband applications[68].…”

mentioning

confidence: 99%

Terahertz Metamaterials for Free-Space and on-Chip Applications: From Active Metadevices to Topological Photonic Crystals

Xing

Fan

et al. 2022

Adv Devices Instrum

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“…Contrary to the conventional electric and magnetic multipoles obtained through the Taylor series expansion of the electromagnetic potentials, toroidal multipoles are derived from the temporal derivative of these potentials and fields. These electromagnetic modes are visualized in terms of currents being distributed on the surface of a torus, namely toroidal currents flowing along the median of the toroid, where an array of magnetic dipoles originating from these poloidal surface currents are arranged in head-to toe configuration [37]. Owing to the low radiative cross-section, these modes are capable of attaining superior quality (Q-factor) resonant response, hence can pave the way for loss-less 'anapole' moments too.…”

Section: Introductionmentioning

confidence: 99%

Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization

et al. 2023

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Plasmonic metasurfaces have been quite a fascinating framework to invoke transformation of incident electromagnetic waves in recent times. Oftentimes, the building block of these metasurfaces (unit cells) consists of two or more meta-resonators. As a consequence, near-field coupling amongst these constituents may occur depending upon the spatial and spectral separation of the individual elements (meta-resonators). In such coupled structures resonance mode-hybridization can help in explaining the formation and energy re-distribution among the resonance modes. However, the coupling of these plasmonic modes is extremely sensitive to incident probe beam polarization and offers ample scope to harness newer physics. A qualitative understanding of the same can be attained through mode-hybridization phenomena. In this context, here, we have proposed a multi-element metastructure unit cell consisting of split ring and dipole resonators aiming to explore the intricate effects of the polarization dependency of these hybridized modes. Therefore, multi-resonator systems with varied inter-resonator spacings (sp= 3.0, 5.0 and 7.0 μm) are fabricated and characterized in the terahertz domain, showing a decrement in the frequency detuning (δ) by 30% (approx.) for a particular polarization orientation of THz probe beam. However, no such detuning is observed for the other polarization. Further, as an outcome of the strong near-field coupling, the emergence of dual toroidal modes is observed. Excitation of toroidal modes demands thoughtful mode engineering to amplify the response of these otherwise feeble modes. Such modes are capable of strongly confining electromagnetic fields due to higher Quality (Q-) factor. Our experimental studies have shown significant signature of the presence of these modes in the Terahertz (THz) domain, backed up with rigorous numerical investigations along with multipole analysis. The calculated multipole decomposition demonstrates stronger scattering amplitude enhancements (~ 7 times) at both the toroidal modes compared to off-resonant values. Such dual toroidal resonances are capable of superior field confinements as compared to single toroidal mode, and therefore, can potentially serve as an ideal testbed in developing next-generation multi-mode bio-sensors as well as realization of high Q-factor lasing cavities, electromagnetically induced transparency (EIT), non-radiating anapole modes, novel ultrafast switching, and several other applications.

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“…Fortunately, a raft of possibilities to realize tunable MMs have been developed including electrical, magnetic, thermal, and optical stimuli. [40][41][42][43][44][45][46] This, in turn, provides pathways to create reconfigurable BIC MMs.…”

Section: Introductionmentioning

confidence: 99%

Tunable Bound States in the Continuum in a Reconfigurable Terahertz Metamaterial

Huang

Kaj

Chen

et al. 2023

Advanced Optical Materials

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Bound states in the continuum (BIC) is an exotic concept describing systems without radiative loss. BICs are widely investigated in optics due to numerous potential applications including lasing, sensing, and filtering, among others. This study introduces a structurally tunable BIC terahertz metamaterial fabricated using micromachining and experimentally characterized using terahertz time domain spectroscopy. Control of the bending angle of the metamaterial by thermal actuation modifies the capacitance enabling tuning from a quasi‐BIC state with a quality factor of 26 to the BIC state. The dynamic response from the quasi‐BIC state to the BIC state is achieved by blueshifting the resonant frequency of the LC mode while maintaining a constant resonant frequency for the dipole mode. Additional insight into the tunable electromagnetic response is obtained using temporal coupled mode theory (CMT). The results reveal the effectiveness of bi‐layer cantilever‐based structures to realize tunable BIC metamaterials with potential applications for nonlinear optics and light‐matter control at terahertz frequencies.

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Tunable Toroidal Response in a Reconfigurable Terahertz Metamaterial

Abstract: as a dielectric, with a permittivity of ε = 7 between 0.6 and 1.0 THz. The surface current and H-field distributions were extracted using an H-field/ surface current monitor at the targeted frequency.

Cited by 13 publications

References 57 publications

Terahertz Metamaterials for Free-Space and on-Chip Applications: From Active Metadevices to Topological Photonic Crystals

Terahertz Metamaterials for Free-Space and on-Chip Applications: From Active Metadevices to Topological Photonic Crystals

Accessing dual toroidal modes in terahertz plasmonic metasurfaces through polarization-sensitive resonance hybridization

Tunable Bound States in the Continuum in a Reconfigurable Terahertz Metamaterial

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