Nonreciprocal active metamaterials

Popa, Bogdan Ioan; Cummer, Steven A.

doi:10.1103/physrevb.85.205101

Cited by 72 publications

(36 citation statements)

References 30 publications

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“…3, 4 The tailored microstructure of such metamaterials has to be much smaller than the wavelength, and this makes it very challenging to realize the desired magnetic properties for optical frequencies. Even though several studies have made approximations to ideal cloaking [5][6][7][8] and all-dielectric carpet cloaking has been demonstrated, 9 nobody has systematically addressed the intriguing question: "How efficiently can we cloak when using conventional simple isotropic dielectric media readily available in nature? "…”

Section: Topology Optimized Low-contrast All-dielectric Optical Cloakmentioning

confidence: 99%

Topology optimized low-contrast all-dielectric optical cloak

Andkjær¹,

Sigmund²

2011

Applied Physics Letters

138

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A systematic methodology for designing low-contrast all-dielectric cloaks operating in the optical range is presented. Topology optimization is used to find the layout of standard dielectric material that minimizes the norm of the scattered field in the surroundings of the cloak. Rotational symmetries are exploited to optimize for multiple angles based on the solution for a single angle of incidence. For a few discrete angles of incidences (1–4) the cloaking is shown to be nearly perfect in a limited frequency range, and even for a rotational symmetric design, cloak and object appear smaller than the noncloaked object.

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Section: Topology Optimized Low-contrast All-dielectric Optical Cloakmentioning

confidence: 99%

Topology optimized low-contrast all-dielectric optical cloak

Andkjær¹,

Sigmund²

2011

Applied Physics Letters

138

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“…Metamaterial concepts have been shown to provide the right platform for the design of non-reciprocal electromagnetic media 22 . In this article, we nontrivially extend this methodology to acoustics, and describe a design approach that results in structures highly subwavelength, but strongly non-reciprocal for their size.…”

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confidence: 99%

Non-reciprocal and highly nonlinear active acoustic metamaterials

2014

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Unidirectional devices that pass acoustic energy in only one direction have numerous applications and, consequently, have recently received significant attention. However, for most practical applications that require unidirectionality at audio and low frequencies, subwavelength implementations capable of the necessary time-reversal symmetry breaking remain elusive. Here we describe a design approach based on metamaterial techniques that provides highly subwavelength and strongly non-reciprocal devices. We demonstrate this approach by designing and experimentally characterizing a non-reciprocal active acoustic metamaterial unit cell composed of a single piezoelectric membrane augmented by a nonlinear electronic circuit, and sandwiched between Helmholtz cavities tuned to different frequencies. The design is thinner than a tenth of a wavelength, yet it has an isolation factor of 410 dB. The design method generates relatively broadband unidirectional devices and is a good candidate for numerous acoustic applications.

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“…Though there is some omega coupling present in the proposed unit cell, as evidenced by the Bloch impedance changing slightly with the propagation direction, it is very weak. In other suggested realizations ( [3,5,8]), the effect of other bianisotropic coupling phenomena (chiral coupling, omega coupling) is much more prominent. It was shown that the velocity parameter V can be varied without affecting the effective refractive index of the medium by simply changing the coupling between two inductors.…”

Section: Discussionmentioning

confidence: 96%

“…Therefore, our model when considering a finite slab corresponds, in fact, to a medium which is moving, but its boundaries remain stationary, similar to the movement of a conveyor belt (the other side of which is hidden from view). Obviously, this is also the case for any artificial realization of moving media lacking nonlinear elements or materials (e.g., [3,5,8]). …”

Section: Proposed Unit Cellmentioning

confidence: 98%

Transmission lines emulating moving media

Vehmas

Hrabar

Tretyakov

2014

2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS)

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In this paper, we show how the electromagnetic phenomena in moving magnetodielectric media can be emulated using artificial composite structures at rest. In particular, we introduce nonreciprocal periodically loaded transmission lines, which support waves obeying the same rules as plane electromagnetic waves in moving media. Because the actual physical structure is at rest, in these transmission lines there are no fundamental limitations on the velocity values, which may take values larger than the speed of light or even complex values (considering complex amplitudes in the time-harmonic regime). An example circuit of a unit cell of a 'moving' transmission line is presented and analyzed both numerically and experimentally. The special case of a composite right-/lefthanded host line is also studied numerically. Besides the fundamental interest, the study is relevant for potential applications in realizing engineered materials for various transformations of electromagnetic fields.

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Nonreciprocal active metamaterials

Cited by 72 publications

References 30 publications

Topology optimized low-contrast all-dielectric optical cloak

Topology optimized low-contrast all-dielectric optical cloak

Non-reciprocal and highly nonlinear active acoustic metamaterials

Transmission lines emulating moving media

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