Finite-wavelength effects in composite media

Egan, Walter G.; Aspnes, D. E.

doi:10.1103/physrevb.26.5313

Cited by 46 publications

(26 citation statements)

References 39 publications

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“…A fundamental constraint of these metamaterials is that the defined features need to be sufficiently small that they act as a simple dielectric material. This requires the pitch of the cuts to be less than about half the wavelength [10,11]. For a given geometry, increasing the frequency beyond this breakdown frequency will lead to scattering and a rapid degradation in performance.…”

Section: Constraintsmentioning

confidence: 99%

Pushing the Limits of Broadband and High-Frequency Metamaterial Silicon Antireflection Coatings

et al. 2018

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Broadband refractive optics realized from high index materials provide compelling design solutions for the next generation of observatories for the Cosmic Microwave Background (CMB), and for sub-millimeter astronomy. In this paper, work is presented which extends the state of the art in silicon lenses with metamaterial antireflection (AR) coatings towards larger bandwidth and higher frequency operation. Examples presented include octave bandwidth coatings with less than 0.5% reflection, a prototype 4:1 bandwidth coating, and a coating optimized for 1.4 THz. For these coatings the detailed design, fabrication and testing processes are described as well as the inherent performance trade offs. Keywords Optics, Metamaterials IntroductionCurrent and planned ground-based CMB experiments [1-5] and sub-millimeter observatories [6, 7] use photon noise limited detectors. Improving the sensitivity of these instruments requires deploying a greater number of detectors. The two approaches being pursued are development of optical systems with large fields of view, and multichroic detectors. The former usually requires lenses fabricated from high index of refraction materials. The latter requires optical systems operating over broad bandwidths. Simultaneously meeting these design requirements necessitates the realization of high performance AR coatings.Silicon lenses with metamaterial AR coatings represent a rapidly maturing technology that can meet these needs. These coatings offer excellent optical performance (low reflection, low dielectric losses, and low scattering [8]), are robust to thermal cycling, and can be

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Section: Constraintsmentioning

confidence: 99%

Pushing the Limits of Broadband and High-Frequency Metamaterial Silicon Antireflection Coatings

et al. 2018

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“…The dielectric function of composite media can be calculated using the effective medium approximation (EMA), if the size of the distinct phases is significantly smaller than the wavelength of illuminating light. It has been shown by Egan and Aspnes that the EMA is considerably influenced for component sizes approaching the wavelength [8]. Recently, we showed that this effect can be used for the estimation of silicon nanosphere sizes comparable to the wavelength [4].…”

Section: Introductionmentioning

confidence: 96%

“…Although there might be a range of other useful algorithms to determine the boundary between the good-fit and bad-fit regions (wavelength λ q corresponding to the quasi-static limit of EMA [8]), an unambiguous method is the calculation of the second derivative of the mean square error (MSE)…”

Section: Resolving Lateral Featuresmentioning

confidence: 99%

Resolving lateral and vertical structures by ellipsometry using wavelength range scan

Petrik¹,

Agócs²,

Volk³

et al. 2014

Thin Solid Films

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For most thin film structures, when changing the wavelength range to fit ellipsometric spectra, the values of the fitted parameters also change to a certain extent. The reason is that compared with the ellipsometric sensitivity many thin films are vertically non-uniform. In absorbing films with significant dispersion in the used wavelength range the penetration depth of probing light can show large variations depending on the wavelength. Consequently, the value of a fitted parameter for a certain wavelength range is a weighted sum of structural information over different depth ranges corresponding to the different wavelengths. When changing the wavelength range, the range of penetration depths can be adjusted. Next, the fitted values can be plotted as a function of the probed depth range calculated directly from the determined or tabulated extinction coefficients. We demonstrate the results on effects is when the lateral feature sizes approach the wavelength of the probing light. In this case the effective medium method is not valid any more, scattering and depolarization occurs. When scanning the wavelength range, the limit wavelength of the onset of scattering can be found, and used for the determination of the corresponding critical lateral period length.

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“…Here, the optical properties of the matrix and hence the propagation of an electromagnetic wave can be tailored with a filler that is smaller than the wavelength of light. When, however, the heterogeneities approach the wavelength in size, they begin to scatter light rather than modulate it (Egan & Aspnes, 1982). The whole process is analogous to the scattering of X-rays by crystals.…”

Section: Composite Scalingmentioning

confidence: 99%

Crystals and composites

Newnham¹,

Trolier-McKinstry²

1990

J Appl Cryst

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This paper is a review of the symmetry and connectivity of composite materials with particular emphasis on the effect that these have on composite properties. Analogies are drawn between composites and crystal structures to demonstrate the similarities between microscopic and macroscopic connectivity. A notation for composite transitions which can be used to describe changes in symmetry and connectivity is also presented.

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Finite-wavelength effects in composite media

Cited by 46 publications

References 39 publications

Pushing the Limits of Broadband and High-Frequency Metamaterial Silicon Antireflection Coatings

Pushing the Limits of Broadband and High-Frequency Metamaterial Silicon Antireflection Coatings

Resolving lateral and vertical structures by ellipsometry using wavelength range scan

Crystals and composites

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