Dielectric and optical properties close to the percolation threshold

Apart from a reflecting and a transparent state, rare-earth-Mg alloys ͑RE-Mg͒ exhibit also a highly absorbing, black state during loading with hydrogen. The occurrence of such a black state is due to the disproportionation into subwavelength size REH 2ϩ⑀ and Mg grains during the first hydrogen loading. While the optical properties of REH x change continuously with a further increase in hydrogen concentration x, Mg changes abruptly from a good reflector to a transparent insulator (MgH 2 ). Thin pure Mg films also show this black state when ͑un͒loaded carefully at elevated temperatures. By using the Bruggeman effective medium approximation in combination with the transfer matrix method it is shown that the coexistence of Mg and MgH 2 grains is the cause of this high absorption. Furthermore, we compare this phenomenon to the high absorption of light observed in metal-dielectric composites.

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“…54,27 This electrical threshold is also observed in the optical absorption at low energies when →0 ͑see Fig. 13͒.…”

Section: →0mentioning

confidence: 80%

Highly absorbing black Mg and rare-earth-Mg switchable mirrors

2004

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“…A generalisation of eq. (2.10) shows that the resonance condition now reads 2) where N is an n S × n S matrix, defined by…”

Section: Discussionmentioning

confidence: 99%

“…The dimensionless complex ratio of the conductances of both phases, 2) and the concentration p are the essential parameters of the model.…”

Section: Introductionmentioning

confidence: 99%

“…The dielectric component is modelled by perfect capacitors, while the metallic bonds consist of a resistance in the first case, of an inductance in series with a resistance in the second case. The RL − C model has been proposed to describe optical properties of several kinds of inhomogeneous materials, such as cermets [2]. These materials undergo an optical transition at some value p * > p c of the metallic fraction, where their dielectric constant changes over from inductive to capacitive.…”

Section: Introductionmentioning

confidence: 99%

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Dielectric resonances of lattice animals and other fractal clusters

Clerc

Giraud

Luck

et al. 1996

J. Phys. A: Math. Gen.

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Abstract. Electrical and optical properties of binary inhomogeneous media are currently modelled by a random network of metallic bonds (conductance σ 0 , concentration p) and dielectric bonds (conductance σ 1 , concentration 1 − p). The macroscopic conductivity of this model is analytic in the complex plane of the dimensionless ratio h = σ 1 /σ 0 of the conductances of both phases, cut along the negative real axis. This cut originates in the accumulation of the resonances of clusters with any size and shape. We demonstrate that the dielectric response of an isolated cluster, or a finite set of clusters, is characterised by a finite spectrum of resonances, occurring at well-defined negative real values of h, and we define the cross-section which gives a measure of the strength of each resonance. These resonances show up as narrow peaks with Lorentzian line shapes, e.g. in the weakdissipation regime of the RL − C model. The resonance frequencies and the corresponding cross-sections only depend on the underlying lattice, on the geometry of the clusters, and on their relative positions. Our approach allows an exact determination of these characteristics. It is applied to several examples of clusters drawn on the square lattice. Scaling laws are derived analytically, and checked numerically, for the resonance spectra of linear clusters, of lattice animals, and of several examples of self-similar fractals.

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“…A typical system is composed of nonlinear (or linear) metallic particles randomly embedded in a linear (or nonlinear) dielectric host. A detailed analysis of the properties of a metal-dielectric composite reveals the existence of many interesting phenomena such as optical bistability [4] and optical percolation threshold [5]. Many authors have devoted themselves to the discussion of the nonlinear optical properties of such composite media.…”

Section: Introductionmentioning

confidence: 99%

Temperature effect on nonlinear optical response of metal–dielectric composite with interfacial layers

Huang¹,

Gao²,

2000

Solid State Communications

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The dependence of nonlinear optical response on temperature is investigated theoretically for a metal-dielectric composite with interfacial layers in a dilute limit. We show that the effect of interfacial layers on the nonlinear optical response of such composites is more prominent at low temperatures than at high temperatures, that the interfacial factor depends on the volume fraction of metallic particles and the frequency of the incident wave, and that an optimal interfacial layer is found for which the nonlinear optical response is able to be enhanced to a maximal. It is shown that weak nonlinearity can be greatly enhanced if the interfacial factor, frequency and volume fraction are chosen appropriately. ᭧

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Dielectric and optical properties close to the percolation threshold

Cited by 55 publications

References 38 publications

Highly absorbing black Mg and rare-earth-Mg switchable mirrors

Highly absorbing black Mg and rare-earth-Mg switchable mirrors

Dielectric resonances of lattice animals and other fractal clusters

Temperature effect on nonlinear optical response of metal–dielectric composite with interfacial layers

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