Perfectly reflectionless omnidirectional absorbers and electromagnetic horizons

Sainath, Kamalesh; Teixeira, Fernando L.

doi:10.1364/josab.32.001645

Cited by 18 publications

(3 citation statements)

References 28 publications

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“…Recently, the asymmetric control of lights has been explored based on several unconventional techniques, such as the optical parity-time symmetric media [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], the designed non-reflecting dielectric profiles [20][21][22], transformation optical media [23][24][25][26], and supersymmetric optical structure media [27,28]. However, these media require inevitable regimes of gain or anisotropy, making it challenging in the experimental implementation.…”

Section: Introductionmentioning

confidence: 99%

Spatial Kramers-Kronig relation and unidirectional light reflection induced by Rydberg dipole-dipole interactions

Zheng¹,

Zhang²,

Liu³

et al. 2021

Preprint

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For tunable control of asymmetric light reflection, we propose a Rydberg atomic system of the optical response varying in space induced by the long-range position-dependent Rydberg dipoledipole interaction either in the type of self-van der Waals dipole-dipole interaction or the cross Förster-like dipole-dipole exchange interaction. In such a one-dimensional system consisting of a control atomic driven upon the Rydberg state and a homogeneous target atomic ensemble, the nonlocalized action from the control atom on the target atoms gradually decreases with the distance between the control and target atoms. Our scheme yields a nonlinear correspondence from a finite spectra range to a finite spatial range of susceptibility via the nonlinear characteristics of Rydberg interaction relative to the position. Therefore, the asymmetric reflection can be induced via the spatial modulation on the target ensemble. In particular, the reflection from one direction can be completely suppressed when the absorption and dispersion parts of the susceptibility are modulated to satisfy the spatial Kramers-Kronig relation in an infinite spectral range. The opposite reflection exhibits a band of a small nonzero reflectivity due to the realistic restriction of the cold atomic density of a relatively small value. Thus, via trapping the target atoms in the optical lattice for the Bragg scattering, we enhance the nonzero reflection obviously and retain the directional reflectionlessness.

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Section: Introductionmentioning

confidence: 99%

Spatial Kramers-Kronig relation and unidirectional light reflection induced by Rydberg dipole-dipole interactions

Zheng¹,

Zhang²,

Liu³

et al. 2021

Preprint

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“…Noteworthy examples of CTOderived media are perfectly matched layers (PMLs), which are reflectionless absorbers extensively used to truncate the spatial domain in computational simulations [11][12][13]. Although their introduction was initially motivated strictly by simulation needs, PMLs also serve as blueprints for anisotropic absorbers [3,[13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Launching and controlling Gaussian beams from point sources via planar transformation media

2018

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Based on operations prescribed under the paradigm of Complex Transformation Optics (CTO) [1][2][3][4], it was recently shown in [5] that a complex source point (CSP) can be mimicked by a paritytime (PT ) transformation media. Such coordinate transformation has a mirror symmetry for the imaginary part, and results in a balanced loss/gain metamaterial slab. A CSP produces a Gaussian beam and, consequently, a point source placed at the center of such metamaterial slab produces a Gaussian beam propagating away from the slab. Here, we extend the CTO analysis to nonsymmetric complex coordinate transformations as put forth in [6] and verify that, by using simply a (homogeneous) doubly anisotropic gain-media metamaterial slab, one can still mimic a CSP and produce Gaussian beam. In addition, we show that a Gaussian-like beams can be produced by point sources placed outside the slab as well [6]. By making use of the extra degrees of freedom (real and imaginary part of the coordinate transformation) provided by CTO, the near-zero requirement on the real part of the resulting constitutive parameters can be relaxed to facilitate potential realization of Gaussian-like beams. We illustrate how beam properties such as peak amplitude and waist location can be controlled by a proper choice of (complex-valued) CTO Jacobian elements. In particular, the beam waist location may be moved bidirectionally by allowing for negative entries in the Jacobian (equivalent to inducing negative refraction effects). These results are then interpreted in light of the ensuing CSP location.

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“…In fact, the perfectly matched layers (PMLs), previously defined mathematically in computational electromagnetics 6 , 7 , can also be considered as absorptive transformation-optics media 8 . However, during any complex coordinate transform, the generation of a gain region is inevitable 9 . Constrained by the intrinsic causality/stability issue, the physical implementation of an absorptive transformation optics medium together with a gain medium satisfying a strict anisotropic dispersion is challenging.…”

Section: Introductionmentioning

confidence: 99%

Observation of reflectionless absorption due to spatial Kramers–Kronig profile

Cao

Zhou

et al. 2017

Nat Commun

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As a fundamental phenomenon in electromagnetics and optics, material absorption has been extensively investigated for centuries. However, omnidirectional, reflectionless absorption in inhomogeneous media has yet to be observed. Previous research on transformation optics indicated that such absorption cannot easily be implemented without involving gain media. A recent theory on wave propagation, however, implies the feasibility to implement such absorption requiring no gain, provided that the permittivity profile of this medium can satisfy the spatial Kramers–Kronig relations. In this work, we implement such a profile over a broad frequency band based on a novel idea of space–frequency Lorentz dispersion. A wideband, omnidirectionally reflectionless absorption is then experimentally observed in the gigahertz range, and is in good agreement with theoretical analysis and full-wave simulations. The proposed method based on the space–frequency dispersion implies the practicability to construct gain-free omnidirectionally non-reflecting absorbers.

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Perfectly reflectionless omnidirectional absorbers and electromagnetic horizons

Cited by 18 publications

References 28 publications

Spatial Kramers-Kronig relation and unidirectional light reflection induced by Rydberg dipole-dipole interactions

Spatial Kramers-Kronig relation and unidirectional light reflection induced by Rydberg dipole-dipole interactions

Launching and controlling Gaussian beams from point sources via planar transformation media

Observation of reflectionless absorption due to spatial Kramers–Kronig profile

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