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

Heinzel, Angelika; Boerner, Volkmar; Gombert, A.; Bläsi, Bénédikt; Wittwer, V.; Luther, Joachim

doi:10.1080/095003400428177

Cited by 49 publications

(49 citation statements)

References 11 publications

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“…Recently, periodic microstructures including photonic crystals have been shown to enable tuning of the spectral distribution of TR [1][2][3][4][5]. Furthermore, polarization properties of TR can be tuned by planar gratings [6,7], photonic crystals [8] and elongated nano-heaters [9].…”

Section: Introductionmentioning

confidence: 99%

Polarized thermal radiation by layer-by-layer metallic emitters with sub-wavelength grating

Lee¹,

Leung²,

Kim³

et al. 2008

Opt. Express

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Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 µm, as well as high emissivity up to 0.65 at a wavelength of 3.7µm. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electricfield is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization. Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 µm, as well as high emissivity up to 0.65 at a wavelength of 3.7µm. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization. Keywords

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Section: Introductionmentioning

confidence: 99%

Polarized thermal radiation by layer-by-layer metallic emitters with sub-wavelength grating

Lee¹,

Leung²,

Kim³

et al. 2008

Opt. Express

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“…26 These filters essentially reflect the low-energy photons back to the selective emitter, in a process known as photon recycling. [27][28][29][30][31][32] In order to achieve sufficient photon recycling, proximity between the emitter and filter is required. 33 In the typical cold-side filter configurations, where the filter is attached to the PV diode as an entire receiver, this requirement can be quantified by the view factor from the emitter to the receiver, which is the probability that emitted photons reach the receiver.…”

Section: Introductionmentioning

confidence: 99%

Integrated photonic crystal selective emitter for thermophotovoltaics

2016

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Abstract. Converting blackbody thermal radiation to electricity via thermophotovoltaics (TPV) is inherently inefficient. Photon recycling using cold-side filters offers potentially improved performance but requires extremely close spacing between the thermal emitter and the receiver, namely a high view factor. Here, we propose an alternative approach for thermal energy conversion, the use of an integrated photonic crystal selective emitter (IPSE), which combines twodimensional photonic crystal selective emitters and filters into a single device. Finite difference time domain and current transport simulations show that IPSEs can significantly suppress sub-bandgap photons. This increases heat-to-electricity conversion for photonic crystal based emitters from 35.2 up to 41.8% at 1573 K for a GaSb photovoltaic (PV) diode with matched bandgaps of 0.7 eV. The physical basis of this enhancement is a shift from a perturbative to a nonperturbative regime, which maximized photon recycling. Furthermore, combining IPSEs with nonconductive optical waveguides eliminates a key difficulty associated with TPV: the need for precise alignment between the hot selective emitter and cool PV diode. The physical effects of both the IPSE and waveguide can be quantified in terms of an extension of the concept of an effective view factor.

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“…5,[19][20][21] The first method is expensive and limited in throughput and area; the second one is capable of exposing large areas, but is inherently limited to simple patterns such as square lattices of cylindrical cavities. In this study, nanoimprint lithography (NIL) was used as a high-throughput, high-resolution nanostructuring technique that allows for complex and dense patterns to be replicated from a master stamp with high reproducibility and uniformity over large areas.…”

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confidence: 99%

“…In the past, PhCs from refractory metals have been used for spectrally selective solar absorbers and thermal emitters. [5][6][7][8][9][10] Refractory metals are ideally suited to achieve thermal stability over long lifetimes due to their high melting point and low vapor pressure. Thermal stability of the nanostructured PhCs is critical 11 and it has been demonstrated that 2D and 3D PhCs with critical dimensions below 100 nm are stable at temperatures exceeding 1200 K by using surface protection coatings of hafnium oxide (HfO2).…”

mentioning

confidence: 99%

Nanoimprinted superlattice metallic photonic crystal as ultraselective solar absorber

Rinnerbauer¹,

Lausecker²,

Schäffler³

et al. 2015

Optica

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A two-dimensional superlattice metallic photonic crystal (PhC) and its fabrication by nanoimprint lithography on tantalum substrates are presented. The superior tailoring capacity of the superlattice PhC geometry is used to achieve spectrally selective solar absorbtion optimized for high temperature and high efficiency solar energy conversion applications. The scalable fabrication route by nanoimprint lithography allows for a highthroughput and high-resolution replication of this complex pattern over large areas. Despite the high fill factor, the pattern of polygonal cavities is accurately replicated into a resist that hardens under ultra-violet radiation over an area of 10 mm 2 . In this way, cavities of 905 nm and 340 nm width are achieved with a period of 1 µm. After pattern transfer into tantalum via a deep reactive ion etching process, the achieved cavities are 2.2 µm deep, separated by 85-95 nm wide ridges with vertical sidewalls. The room temperature reflectance spectra of the fabricated samples show excellent agreement with simulated results, with a high spectral absorptance approaching blackbody absorption in the range from 300-1900 nm, and a steep cut-off. The calculated solar absorptivity of this superlattice PhC is 96% and its thermal transfer efficiency is 82.8% at an operating temperature of 1500 K and an irradiance of 1000 kW/m2. © 2015 Optical Society of America In the last decade, the field of high-temperature photonics is growing rapidly due to an increased scientific interest as well as emerging applications, especially in the field of energy conversion. In this field, the challenges photonic components have to meet are high temperature stability over long lifetimes, high tailoring capacity of the optical properties, and economic fabrication over large areas. In this study, a superlattice PhC consisting of polygonal cavities gave superior control over the spectral properties to achieve a highly selective solar absorber with low thermal emission for high temperature energy conversion applications. For the first time, a metallic superlattice PhC absorber was fabricated by nanoimprint lithography (NIL) as a highthroughput, high-resolution technique paving the way for complex high-temperature photonic components on a large scale. Selective thermal absorbers and emitters are critical components for high temperature and high-efficiency energy conversion applications, such as thermophotovoltaics (TPV), solar TPV, and solar thermal systems. TPV is a thermal-to-electrical energy conversion scheme where thermal emission from a hot radiation source (emitter) drives a suitable photovoltaic cell, promising low maintenance, scalability, high power densities as well as flexibility regarding the employed fuel. In solar TPV (STPV), the irradiation from the sun on an absorber is converted into narrow-band thermal radiation on the emitter side. 1 To reach the high efficiencies predicted by theoretical studies 2-4 it is crucial to (1) reach high operating temperatures (>1000 K) and (2) to employ spectrally select...

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

Cited by 49 publications

References 11 publications

Polarized thermal radiation by layer-by-layer metallic emitters with sub-wavelength grating

Polarized thermal radiation by layer-by-layer metallic emitters with sub-wavelength grating

Integrated photonic crystal selective emitter for thermophotovoltaics

Nanoimprinted superlattice metallic photonic crystal as ultraselective solar absorber

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