Far-IR optical properties of freestanding and dielectrically backed metal meshes

Durschlag, M.S.; DeTemple, T. A.

doi:10.1364/ao.20.001245

Cited by 67 publications

(12 citation statements)

References 32 publications

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“…This type of ® lter is widely used in microwave technology [3,4]. It has also been investigated for the far IR [5,6], the NIR [7], for solar applications [8] and for the visible spectral range [9]. Generally, the optical properties of metals change dramatically in the NIR and the visible spectral range, due to the excitation of interband transitions.…”

Section: Introductionmentioning

confidence: 99%

Radiation filters and emitters for the NIR based on periodically structured metal surfaces

Heinzel

Boerner

Gombert

et al. 2000

Journal of Modern Optics

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The spectrally selective optical properties of wavelength selective radiation emitters and ® lters based on periodically microstructured metal surfaces were investigated. Metal surfaces were structured by the use of a holographic mask and subsequent etching processes. Due to the microstructure, thermally excited surface plasmons couple to electromagnetic radiation. Therefore a structured tungsten surface can act as a selective radiation emitter. The calculation of the absorptance by a rigorous diå raction theory allows the prediction of the emissivity of such structures. The angle dependent emissivity of tungsten gratings with periods of 1.4 m m and 2.0 m m was measured. A peak emissivity of 70%at a wavelength of 1.6 m m was achieved. Band pass ® lters for the near infrared spectral range based on perforated metal ® lms were investigated theoretically and experimentally. Filters with a grating period of 2.0 m m were produced. A peak transmittance of 80% at a wavelength 2.9 m m was achieved. The optical properties of the diå ractive elements described partly show a strong angle dependence IntroductionIn this contribution we investigate the optical properties of periodically microstructured metallic surfaces. The goal is to manufacture radiation ® lters and emitters for the near infrared (NIR) spectral range, that show wavelengthselective optical properties based on resonance eå ects.Our work was initially motivated by the use of selective emitters and bandpass ® lters in thermophotovoltaic (TPV) systems [1]. In a TPV generator, a thermal emitter is driven by any heat source with a suae cient temperature. The radiation of the emitter is converted into electrical energy by a photovoltaic (PV) cell. One of the major challenges of current research work on TPV systems is to reduce the mismatch between the emission spectrum and the spectral sensitivity of the PV cell. This can be done by increasing the emissivity of the emitter at convertible photon energies and by ® ltering the radiation.The selective emitters which we investigated are based on the eå ect that on structured surfaces thermally excited surface plasmons can be converted to electromagnetic radiation. This leads to an increase of the emittance of a metallic surface in a limited spectral range. The kind of surface structure determines the spectral range of the emissivity maxima. Towards longer wavelengths the grating

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Section: Introductionmentioning

confidence: 99%

Radiation filters and emitters for the NIR based on periodically structured metal surfaces

Heinzel

Boerner

Gombert

et al. 2000

Journal of Modern Optics

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“…Computation of is the central problem in the theory of dielectrics. According to the classical theory applied here [21], the local field for spherical inclusions is (5) Since the polarization is also , the effective permittivity of the composite is associated with the polarizability of individual inclusions according to the Maxwell Gar- nett equation (also known as the Clausius Mossotti equation) [19], [20] ( 6) where is the volume fraction given in terms of the number density of scatterers (7) and is the normalized polarizability of the inclusions defined as (8) The static polarizability of the coated sphere is [17] (9), shown at the bottom of the next page, where is the concentric volume ratio. Inputing this value into the Maxwell Garnett equation (6) yields the effective permittivity for the composite.…”

Section: B Effective Medium Analysismentioning

confidence: 99%

“…Applications range from the microwave region in multiband antenna systems, narrowband reflectors, radomes for active radar systems, RF absorbers [1]- [7], up to the far and near infrared portion of the spectrum as mirrors in molecular lasers, polarizers, and solar selective surfaces [8]- [10]. However, existing FSS suffer from three major drawbacks.…”

Section: Introductionmentioning

confidence: 99%

Novel material with narrow-band transparency window in the bulk

Kyriazidou

Díaz

Alexopoulos

2000

IEEE Trans. Antennas Propagat.

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This paper presents the theoretical design of an artificial dielectric exhibiting narrowband frequency selective properties in the bulk without relying on periodic placement of elements. In this manner, it initiates a novel approach that bypasses the drawbacks of the traditional frequency selective surfaces (FSS), namely, unwanted passbands, dependence on excitation angle and polarization, and difficulties in conversion from planar to curved geometries. The key design elements are the concentric geometry of the inclusions and the use of Lorentzian resonant media. A discussion of physical resonant materials is presented, substantiating the credibility of the theoretical design. To illustrate the approach, a novel complex medium is synthesized as an ensemble of spherical particles composed of a lossy core coated with a highly resonant dielectric layer and embedded into a dielectric host. The resulting structure is an amorphous substance, lossy over its entire spectrum except for two narrow-band transparency windows, where it may become as lossless as desired. The parameter space of the system is thoroughly analyzed which determines the type of constitutive materials and geometries for tailor-designing the windows according to specifications (shape, positioning and overall normalization). In this sense, the lossy concentric structure forms an ideal candidate for thin absorbing films (TAF's) with extensive applications in antenna systems, RF absorbers, and anechoic chambers.

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“…Because of their frequency selective properties, FSS are incorporated in a wide variety of applications such as the realization of reflector antennas, radome design, making polarizers and beam splitters, and also as radar absorbing structure [3,[6][7][8][9]. Radar Absorbing Materials (RAM) with FSS can improve absorption characteristic as it has combined characteristics of FSS as well as RAM.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Frequency Selective Surfaces for Radar Absorbing Materials

Singh¹,

Kumar²,

Meena³

et al. 2012

PIER B

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Abstract-Nowadays, applications of Frequency Selective Surfaces (FSS) for radar absorbing materials (RAM) are increasing, but it is still a challenge to select a proper FSS for a particular material as well as the dimensions of FSS for optimized absorption. Therefore, in this paper an attempt has been made to optimize the dimensions of FSS for microwave absorbing application using Genetic Algorithm (GA) approach. The considered frequency selective surfaces are composed of conducting patch elements pasted on the ferrite layer. FSS are used for filtration and microwave absorption. In this work, selection and optimization of FSS with radar absorbing material has been done for obtaining the maximum absorption at 8-12 GHz frequency. An equivalent circuit method has been used for the analysis of different FSS, which is further used to design fitness function of GA for optimizing the dimensions of FSS. Eight different available ferrite materials with frequency dependant permittivities and permeabilities have been used as material database. The GA optimization is proposed to select the proper material out of eight available materials with proper dimensions of FSS. The optimized results suggest the material from database and dimensions of FSS. The selected material is then mixed with epoxy and hardener, and coated over the aluminium sheet. Thereafter, all five FSS were fabricated on ferrite coated Al sheets using photolithographic method followed by wet etching. The absorption was measured for all FSS using absorption testing device (ATD) method at X-band. Absorption results showed that significant amount of absorption enhanced with the addition of proper FSS on radar absorbing coating.

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Far-IR optical properties of freestanding and dielectrically backed metal meshes

Cited by 67 publications

References 32 publications

Radiation filters and emitters for the NIR based on periodically structured metal surfaces

Radiation filters and emitters for the NIR based on periodically structured metal surfaces

Novel material with narrow-band transparency window in the bulk

Analysis of Frequency Selective Surfaces for Radar Absorbing Materials

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