Experimental demonstration of ultra-wideband and high-efficiency terahertz spoof surface plasmon polaritons coupler

Tang, Heng-He; Ma, Tianjun; Liu, Pu‐Kun

doi:10.1063/1.4948928

Cited by 29 publications

(11 citation statements)

References 21 publications

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“…Due to the momentum mismatch between free space waves and SSP mode [46,47], the extracted information carried by SSP is still stuck in the grating surface. Fortunately, in our previous investigations [48], an ultra-broadband SSP coupler has been proposed and demonstrated to alleviate the momentum mismatch.…”

Section: Sampling Spatial Spectrum By Sspmentioning

confidence: 99%

Far-Field Subwavelength Resolution Imaging by Spatial Spectrum Sampling

et al. 2019

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Imaging below the diffraction limit is always a public interest because of the restricted resolution of conventional imaging systems. To beat the limit, evanescent harmonics decaying in space must participate in the imaging process. Here, we introduce the method of spatial spectrum sampling, a novel far-field superresolution imaging method for microwave and terahertz regime. Strong dispersion and momentum conservation allow the spoof surface plasmon polaritons (SSP) structure to become a sensitive probe for spatial harmonics. This enables that the spatial information of the targets including both propagating and evanescent components, can be extracted by tuning and recording SSP in the far field. Then, the subwavelength resolution is constructed by the inversed Fourier transform of the sampled spatial spectrum. Using the modified subwavelength metallic grating as the probe, a far-field resolution of 0.17 is numerically and experimentally verified, and two-dimensional imaging ability is also fully discussed. The imaging ability and flexibility can be further optimizing the SSP structures.We are confident that our working mechanism will have great potentials in the superresolution imaging applications in the microwave and terahertz frequency range. IntroductionAchieving spatial resolution without limited by the working wavelength always attracts tremendous attention, due to the pervasive applications of imaging. However, the diffraction limit indicates the fine features smaller than half a wavelength are carried by the evanescent harmonics [1], whose amplitude exponentially decays with distance. The contribution of these harmonics is negligible when the imaging distance larger than a wavelength. To circumvent the inherent limitation, the optical elements should own ability of capturing the evanescent part of spatial information. By mechanically canning a sensitive probe, the near-field microscope (NFSM) [2-4] can well surpass the diffraction limit for thousand times, but the imaging operation is very time-wasting. To obtain superresolution images in a single shot, the concept of perfect lens is theoretically exploited by Pendry [1], utilizing the plasmonic effect in materials to enhance the evanescent waves [5,6]. Soon after this imaging method is experimentally verified at optical wavelength by plasmonic slabs, such as the noble metal [7,8] and dielectrics [9]. Although the imaging ability of such lenses can be further enhanced by other methods [10], the working distance is still subject to the near field [11,12]. A remarkable device, termed hyperlens, is capable of converting the evanescent harmonics into propagating waves through curved geometry [13][14][15][16] or gratings [17,18].In this way, superresolution pictures are formed in the far field. The hyperlens can be constructed by periodic arrangement of plasmonics materials and common dielectrics [11][12][13][14][15][16][17][18][19][20].When it comes to the longer wavelength, for example, the terahertz domain, which has great potential in non-destructive test...

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Section: Sampling Spatial Spectrum By Sspmentioning

confidence: 99%

Far-Field Subwavelength Resolution Imaging by Spatial Spectrum Sampling

et al. 2019

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“…It is crucial to convert the SSP wave into fast wave, and several approaches are aimed at overcoming this obstacle. For instance, the gradient waveguide and the meta-surface structure could achieve it [17], [18]. However, it is challenging to achieve an effective conversion in an on-chip system because of the limitation of manufacturing difficulties, high-power capacity and electron bombardment.…”

Section: Introductionmentioning

confidence: 99%

Free-Electron-Driven Multi-Frequency Terahertz Radiation on a Super-Grating Structure

Zhu

et al. 2019

IEEE Access

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A free-electron-driven multi-frequency terahertz (THz) radiation based on a super-grating structure is elucidated in this paper. The super-grating, i.e., periodically depth-modulated metallic grating, has a peculiar dispersion characteristic, similar to the energy bands in a crystal due to the Brillouin zone folding effect. The multi-frequency radiation is stimulated in several directions with the excitation of a free electron as the synchronization points are in the radiative region. The radiation frequency can be independently tuned by the groove depths of the super-grating. The number of frequencies is tailored by the modulated period. Additionally, the multi-frequency THz radiation exhibits a frequency-locked effect during the energy variation of the free electron. Moreover, the radiation field intensity shows a significant enhancement compared with that of a conventional Smith-Purcell radiation. The work is promising for developing efficient on-chip THz radiation sources and boosts advanced THz applications such as communications, multi-frequency imaging, and beam diagnostics, etc.

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“…However, due to the large wave vector mismatch between the SSP and free space waves, SSP cannot be excited directly by simply impinging electromagnetic waves (EMWs) on the SSP waveguides. To compensate for the wave vector mismatch, many SSP couplers have been proposed to introduce additional wave vectors, such as depth gradient metal gratings [7,8].…”

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confidence: 99%

Terahertz dual phase gradient metasurfaces: high-efficiency binary-channel spoof surface plasmon excitation

et al. 2020

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Spoof surface plasmon meta-couplers are compact antennas which link propagating waves and surface waves. However, most of them are designed with a fixed phase gradient and channel for the incident waves with specific polarization, which limits their further applications in multichannel scenarios. In this Letter, we propose, to the best of our knowledge, a new method that combines the Brillouin folds theory with the Generalized Snell Law. We demonstrate that when the phase gradient of the metasurface is large enough, Brillouin folds effect will occur, which will create dual phase gradient space in a single metasurface. With this method, we design two novel terahertz meta-couplers with functionalities of symmetrical and asymmetrical binary-channel/bidirectional SSP excitation. Furthermore, finite element method (FEM) simulations are performed to demonstrate their functionalities. Considering the orthogonality of the incident waves, there can be a total of four independent space channels to excite SSP on one metasurface. This work may open up new routes in multi-channel SSP meta-couplers and multi-beam surface wave antennas.

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Experimental demonstration of ultra-wideband and high-efficiency terahertz spoof surface plasmon polaritons coupler

Cited by 29 publications

References 21 publications

Far-Field Subwavelength Resolution Imaging by Spatial Spectrum Sampling

Far-Field Subwavelength Resolution Imaging by Spatial Spectrum Sampling

Free-Electron-Driven Multi-Frequency Terahertz Radiation on a Super-Grating Structure

Terahertz dual phase gradient metasurfaces: high-efficiency binary-channel spoof surface plasmon excitation

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