Space-time gradient metasurfaces

Hadad, Yakir; Sounas, Dimitrios L.; Alù, Andrea

doi:10.1103/physrevb.92.100304

Cited by 372 publications

(278 citation statements)

References 44 publications

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“…[ 167 ] Beside the spatial gradient, a transverse temporal gradient can also be taken into account to break the reciprocity symmetry, which shows important application in nonreciprocal devices, such as optical diode. [ 168 ] More comprehensively, such concept of wave control has been applied to diverse disciplines for wave-matter interactions, such as acoustics, [ 169,170 ] thermal physics, [ 171,172 ] etc.…”

Section: Other Applicationsmentioning

confidence: 99%

Advances in Full Control of Electromagnetic Waves with Metasurfaces

Zhang

Mei

Huang

et al. 2016

Advanced Optical Materials

357

199

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Metasurfaces, two‐dimensional versions of metamaterials, retain the great capabilities of three‐dimensional counterparts in manipulating electromagnetic wave behaviors, while reducing the challenges in fabrication. By judiciously engineering parameters of individual building blocks (such as geometry, size, and material) and selecting specific design algorithms, metasurfaces are promising to replace conventional electromagnetic elements in nanoplasmonic/photonic devices. Significantly, such concept can be readily promoted to other disciplines, such as acoustics, thermal physics, and seismology. In this article, the latest advances in full control of electromagnetic waves with metasurfaces are briefly reviewed from a functionality perspective. A broad avenue towards real‐life applications of metamaterials has been opened up, although they are still at their infant stage. At the end, several promising approaches are suggested to extend the applications of metasurfaces.

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Section: Other Applicationsmentioning

confidence: 99%

Advances in Full Control of Electromagnetic Waves with Metasurfaces

Zhang

Mei

Huang

et al. 2016

Advanced Optical Materials

357

199

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“…The strategy introduced in this paper can be considered as a temporal analogue of the typical space-gradient metasurface [22,23, 24,25,27]. Thus, by combining both strategies one could design an all-optical space-time gradient metasurface to break the geometrical and temporal symmetry on-chip [38,39], design ultrafast temporal holograms, and control the directivity of emission using an optical gate signal [40,41].In summary, we have demonstrated that a metasurface geometry is uniquely suited to achieving large nonlinear refraction. We have shown that a metasurface may exhibit an extremely large intensitydependent refractive index if an epsilon-near-zero medium is incorporated into the design.…”

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confidence: 99%

Large optical nonlinearity of nanoantennas coupled to an epsilon-near-zero material

et al. 2018

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The size and operating energy of a nonlinear optical device are fundamentally constrained by the weakness of the nonlinear optical response of common materials. Here, we report that a 50-nm-thick optical metasurface made of optical dipole antennas coupled to an epsilon-near-zero material exhibits a broadband (∼ 400 nm bandwidth) and ultrafast (recovery time less than 1 ps) intensitydependent refractive index n 2 as large as −3.73 ± 0.56 cm 2 /GW. Furthermore, the metasurface exhibits a maximum optically induced refractive index change of ±2.5 over a spectral range of ∼ 200 nm. The inclusion of low-Q nanoantennas on an epsilon-near-zero thin film not only allows one to design a metasurface with an unprecedentedly large nonlinear optical response but also offers the flexibility to tailor the sign of the response. Our technique allows one to overcome a longstanding challenge in nonlinear optics, namely that of finding a material for which the nonlinear contribution to the refractive index is of the order of unity. It consequently offers the possibility of designing low-power nonlinear nano-optical devices with orders-of-magnitude smaller footprints.All-optical signal processing and computation are often hailed as breakthrough technologies for the next generation of computation and communication devices. Two important parameters of such devices, energy consumption and size, critically depend on 1 the strength of the nonlinear optical response of the materials from which they are made. However, materials typically exhibit an extremely weak nonlinear optical response. This property makes designing subwavelength all-optical active devices extremely difficult. Thus, all-optical active devices tend to have large footprints, which limits the integration density to many orders of magnitude smaller than what can be achieved in a state-of-the-art electronic integrated circuits [1,2]. Thus, materials with much stronger nonlinear optical responses are needed in order to enable integrated high-density on-chip nonlinear optical devices.Over the years several approaches have been explored to enhance the intrinsic nonlinear optical response of materials, including local field enhancement using composite structures [3,4,5], plasmonic structures [6,7], and metamaterials [8,9,10,11]. However, these techniques offer only limited control over the magnitude (and sign when applicable) of the wavelength-dependent nonlinear response, and typically involve a trade-off between the strength of the nonlinearity and the spectral position of the peak nonlinear response. It has been reported recently that materials with vanishingly small permittivitycommonly known as epsilon-near-zero or ENZ material -exhibit intriguing linear [12,13,14,15,16] and large nonlinear responses [17,18,19,20,21]. However, an ENZ material has a large nonlinear response over only a relatively narrow spectral range. Furthermore, the zero-permittivity wavelength, strength of the nonlinear response, and the losses depend on the optical properties of the ENZ material. In com...

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“…The concept is based on imparting a suitable form of momentum biasing that breaks time-reversal symmetry, achieved with mechanical motion or with spatiotemporal modulation (20)(21)(22)(23)(24)(25)(26)(27)(28)(29). In this paper, for the first time to our knowledge, we apply these concepts to emitting/absorbing systems, showing that it is possible to realize magnetic-free nonreciprocal structures that can emit without absorbing from the same direction over a broad frequency range.…”

mentioning

confidence: 99%

Breaking temporal symmetries for emission and absorption

Hadad

Soric

Alù

2016

Proc. Natl. Acad. Sci. U.S.A.

260

177

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Time-reversal symmetries impose stringent constraints on emission and absorption. Antennas, from radiofrequencies to optics, are bound to transmit and receive signals equally well from the same direction, making a directive antenna prone to receive echoes and reflections. Similarly, in thermodynamics Kirchhoff's law dictates that the absorptivity and emissivity are bound to be equal in reciprocal systems at equilibrium, e(ω, θ) = a(ω, θ), with important consequences for thermal management and energy applications. This bound requires that a good absorber emits a portion of the absorbed energy back to the source, limiting its overall efficiency. Recent works have shown that weak time modulation or mechanical motion in suitably designed structures may largely break reciprocity and time-reversal symmetry. Here we show theoretically and experimentally that a spatiotemporally modulated device can be designed to have drastically different emission and absorption properties. The proposed concept may provide significant advances for compact and efficient radiofrequency communication systems, as well as for energy harvesting and thermal management when translated to infrared frequencies.

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Space-time gradient metasurfaces

Cited by 372 publications

References 44 publications

Advances in Full Control of Electromagnetic Waves with Metasurfaces

Advances in Full Control of Electromagnetic Waves with Metasurfaces

Large optical nonlinearity of nanoantennas coupled to an epsilon-near-zero material

Breaking temporal symmetries for emission and absorption

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