Dielectric singularity in hyperbolic metamaterials: the inversion point of coexisting anisotropies

Caligiuri, Vincenzo; Dhama, Rakesh; Sreekanth, Kandammathe Valiyaveedu; Strangi, Giuseppe; Luca, Antonio De

doi:10.1038/srep20002

Cited by 64 publications

(75 citation statements)

References 39 publications

(51 reference statements)

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“…Figure shows that the normalized fluorescence lifetime (τ 1 ) of the dye embedded in the HMM (as a function of the emission wavelength reported as the distance from the transition wavelength Δλ) exhibits a flat trend within the effective‐dielectric range, while it is remarkably reduced within the type II region. The enhancement of the decay rate of a fluorophore positioned in proximity of an HMM has been widely studied in previous works . When entering the type II anisotropy regime, the isofrequency curves deriving from the dispersion relationship given in Equation assume the shape of an open hyperboloid.…”

Section: Resultsmentioning

confidence: 99%

“…Within this frame, the use of the so‐called metamaterials, and in particular of hyperbolic metamaterials (HMMs), represents an intriguing opportunity. HMMs are uniaxial structures manifesting a hyperbolic dispersion relation whose application range spans from hyperlensing to extreme biosensing . In order to describe their optical constants, it is convenient to homogenize the dielectric permittivity of HMMs by using the effective medium theory (EMT).…”

Section: Introductionmentioning

confidence: 99%

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Environmental Control of the Topological Transition in Metal/Photoemissive‐Blend Metamaterials

Caligiuri

Lento

Ricciardi

et al. 2018

Advanced Optical Materials

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intriguing opportunity. HMMs are uniaxial structures manifesting a hyperbolic dispersion relation whose application range spans from hyperlensing to extreme biosensing. [13][14][15][16][17][18][19][20][21][22][23][24] In order to describe their optical constants, it is convenient to homogenize the dielectric permittivity of HMMs by using the effective medium theory (EMT). If the dimensions of the fundamental components of the HMM, that in our case consists of alternated metal/dielectric layer pairs, are chosen to be deeply subwavelength, a uniaxial anisotropy arises, due to the specific periodic arrangement, with the appearance of two distinct values of dielectric permittivity, one parallel (ε || ) and one perpendicular (ε ⊥ ) to the plane of the layersHere t D and t M are the dielectric and metal thickness, respectively, and ε D and ε M their relative dielectric permittivities. Equation (1) reveals that ε || can vanish at a specific wavelength where (ε D /ε M ) = -(t M /t D ). In the resulting regime, known as epsilon-near-zero (ε NZ ), many fascinating phenomena can occur. [25][26][27][28] Unfortunately, once the fundamental componentsThe quest for unconventional optical materials finds natural answers in the field of plasmonics. Here, special composites can manifest singularities in their dielectric permittivity. The so-called epsilon-near-zero (ε NZ ) condition is typically encountered in artificial materials called hyperbolic metamaterials (HMMs). Unfortunately, tuning the HMMs ε NZ is still challenging. Here it is demonstrated how the ε NZ frequency of an HMM can be reversibly tuned via thermally induced water absorption/desorption. The key element is a dielectric hygroscopic material, consisting of a blend of a polymer, a sol-gel unsintered TiO 2 , and an organic dye. Due to the hygroscopic nature of unsintered TiO 2 , an increase of temperature induces a reversible physical contraction of the thickness of the dielectric blend, as well as an increase of refractive index. This causes a remarkable 45 nm shift of the absorption peak of the embedded dye, acting as a chromatic label. When such a blend is embedded in an HMM, a reversible thermal tuning of the overall optical response, as well as an epsilon-near-zero wavelength shift by about 25 nm, is induced. The remarkable tuning range shown here, besides obvious HMM-based temperature sensing applications, paves the way toward a plethora of new functions in which tunable ε NZ materials are needed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Environmental Control of the Topological Transition in Metal/Photoemissive‐Blend Metamaterials

Caligiuri

Lento

Ricciardi

et al. 2018

Advanced Optical Materials

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“…(47) and (53), together with their complex conjugates, constitute a complete set of (complexified) solutions of Maxwell equations in R 3 × I; in other words, the boundary-value problems defined by Eqs. (42,43) and Eqs. (49,50) admit solutions only for (a subset of) ω 2 > 0.…”

Section: A Instability Analysismentioning

confidence: 99%

“…Although it might be tempting not to consider these "runaway" solutions, [25,26], they are essential, if they exist, to expand an arbitrary initial field configuration satisfying the boundaryvalue problems set by Eqs. (42,43) and (49,50); in other words, the stationary modes alone do not constitute a complete set of solutions of Maxwell's equations with the given boundary conditions. And even if, on the classical level, one might want to restrict attention to initial field configurations which have no contribution coming from these unstable modes -which is certainly unnatural, for causality forbids the system to constrain its initial configuration based on its future behavior -, inevitable quantum fluctuations of these modes would grow, making them dominant some time e-foldings (t ∼ N Ω −1 , N ≫ 1) after the proper material conditions having been engineered.…”

Section: A Instability Analysismentioning

confidence: 99%

“…Clearly, the feasibility of such analogues is bound to the existence of material configurations with the required constitutive functions. As briefly pointed out in the introduction, this can be achieved at least for anisotropic neutral plasmas, and the recent advances in metamate-rial science offer a plethora of possible candidates, specially the hyperbolic metamaterials [42,43], that possess precisely the form given in Eqs. (9,10) with the required "negativeness."…”

Section: Final Remarksmentioning

confidence: 99%

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Analogues of gravity-induced instabilities in anisotropic metamaterials

Ribeiro

Vanzella

2020

Phys. Rev. Research

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In the context of field theory in curved spacetimes, it is known that suitable background spacetime geometries can trigger instabilities of fields, leading to exponential growth of their (quantum and classical) fluctuations -a phenomenon called vacuum awakening in the quantum context, which in some classical scenarios seeds spontaneous scalarization/vectorization. Despite its conceptual interest, an actual observation in nature of this effect is uncertain since it depends on the existence of fields with appropriate masses and couplings in strong-gravity regimes. Here, we propose analogues for this gravity-induced instability based on nonlinear optics of metamaterials which could, in principle, be observed in laboratory. * Electronic address: caiocesarribeiro@ifsc.usp.br † Electronic address: vanzella@ifsc.usp.br

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A Subtractive Photoresist Platform for Micro‐ and Macroscopic 3D Printed Structures

Zieger

Müller

Blasco

et al. 2018

Adv Funct Materials

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The selective removal of structural elements plays a decisive role in three-dimensional (3D) printing applications enabling complex geometries. To date, the fabrication of complex structures on the microscale is severely limited by multi-step processes. Herein, we report a subtractive photoresist platform technology that is transferable from microscopic 3D printing via Direct Laser Writing (DLW) to macroscopic structures via Stereolithography (SLA). All resist components are readily accessible and exchangeable, offering fast adaptation of the resist's property profile. The micro-and macroprinted structures can be removed in a facile fashion, without affecting objects based on standard photoresists. The cleavage is analyzed by time-lapse images as well as via in-depth spectroscopic assessment. The mechanical properties of the printed materials are investigated by nanoindentation. Critically, we demonstrate the power of our subtractive resist platform by constructing complex 3D objects with flying features on the microscale.

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Dielectric singularity in hyperbolic metamaterials: the inversion point of coexisting anisotropies

Cited by 64 publications

References 39 publications

Environmental Control of the Topological Transition in Metal/Photoemissive‐Blend Metamaterials

Environmental Control of the Topological Transition in Metal/Photoemissive‐Blend Metamaterials

Analogues of gravity-induced instabilities in anisotropic metamaterials

A Subtractive Photoresist Platform for Micro‐ and Macroscopic 3D Printed Structures

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