Focused thermal emission from a nanostructured SiC surface

Chalabi, Hamidreza; Alù, Andrea; Brongersma, Mark L.

doi:10.1103/physrevb.94.094307

Cited by 49 publications

(28 citation statements)

References 53 publications

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“…Control of the spatial coherence of TE can be generalized to shape the far field of thermal emission in more-complex ways. For example, by patterning an array of antennas with a non-uniform scattering phase distribution on a SiC surface, free-space focusing of TE has been demonstrated [ Fig. 2(e)] 45 . Guided by a similar principle, a non-uniform metasurface composed of thermal emitters with varying angular emissivity patterns was shown to suppress TE into a certain area, forming a "dark spot" 51 .…”

Section: Box 2-critical Couplingmentioning

confidence: 99%

Nanophotonic engineering of far-field thermal emitters

et al. 2019

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Thermal emission is a ubiquitous and fundamental process by which all objects at non-zero temperatures radiate electromagnetic energy. This process is often presented to be incoherent in both space and time, resulting in broadband, omnidirectional light emission toward the far field, with a spectral density related to the emitter temperature by Planck's law. Over the past two decades, there has been considerable progress in engineering the spectrum, directionality, polarization, and temporal response of thermally emitted light using nanostructured materials. This review summarizes the basic physics of thermal emission, lays out various nanophotonic approaches to engineer thermal-emission in the far field, and highlights several relevant applications, including energy harvesting, lighting, and radiative cooling. 2 I: IntroductionEvery hot object emits electromagnetic radiation according to the fundamental principles of statistical mechanics. Examples of this phenomenon-dubbed thermal emission (TE)-include sunlight and the glow of an electric stovetop or embers in a fire. The basic physics behind TE from hot objects has been well understood for over a century, as described by Planck's law 1 , which states that an ideal black body (a fictitious object that perfectly absorbs over the entire electromagnetic spectrum and for all incident angles) emits a broad spectrum of electromagnetic radiation determined by its temperature.Increasing the temperature of a black body results in an increase in emitted intensity, and a skew of the spectral distribution toward shorter wavelengths. A fundamental property of this process is that the thermal emissivity of any object-which quantifies the propensity of that object to generate TE compared to a black body-is determined by its optical absorptivity 1 . The connection between absorption and thermal emission, linked to the time reversibility of microscopic processes, suggests that the temporal and spatial coherence of the TE can be engineered via judicious material selection and patterning.Engineering of TE is of great interest for applications in lighting, thermoregulation, energy harvesting, tagging, and imaging. This review summarizes the basic physics of TE and surveys recent advances in the far-field control of TE via nanophotonic engineering. First, we present the basic formalism that describes TE, and review realizations of narrowband, directional, and dynamically reconfigurable far-field thermal emitters based on nanophotonic structures. Then we review applications of engineered far-field TE, with emphasis on energy and sustainability. II: Theoretical backgroundAt elevated temperatures, the constituents of matter, including electrons and atomic nuclei, possess

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Section: Box 2-critical Couplingmentioning

confidence: 99%

Nanophotonic engineering of far-field thermal emitters

et al. 2019

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“…Thermal emission from objects tends to be spectrally broadband, unpolarized, and temporally invariant. These common notions are now challenged with the emergence of new nanophotonic structures and metasurface concepts that afford on-demand, active manipulation of the thermal emission process [149][150][151][152][153][154][155][156]. The thermal emission spectra of metasurfaces, which are directly connected to their spectral absorption properties through Kirchhoff's law [157], can be engineered with tremendous flexibility through nanostructuring.…”

Section: Open Challenges and Opportunities For Metasurfacesmentioning

confidence: 99%

The road to atomically thin metasurface optics

Brongersma

2020

Nanophotonics

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The development of flat optics has taken the world by storm. The initial mission was to try and replace conventional optical elements by thinner, lightweight equivalents. However, while developing this technology and learning about its strengths and limitations, researchers have identified a myriad of exciting new opportunities. It is therefore a great moment to explore where flat optics can really make a difference and what materials and building blocks are needed to make further progress. Building on its strengths, flat optics is bound to impact computational imaging, active wavefront manipulation, ultrafast spatiotemporal control of light, quantum communications, thermal emission management, novel display technologies, and sensing. In parallel with the development of flat optics, we have witnessed an incredible progress in the large-area synthesis and physical understanding of atomically thin, two-dimensional (2D) quantum materials. Given that these materials bring a wealth of unique physical properties and feature the same dimensionality as planar optical elements, they appear to have exactly what it takes to develop the next generation of high-performance flat optics.

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“…The development of robust inverse-design techniques in recent years has presented a solution to this problem, with examples drawing from holography [21] , machine learning [22] and optimization approaches [23][24][25] . Such concepts have even been applied to the design of thermal emitters for the purpose of improved control of their spectral and spatial emission properties [24,26] . These arguments present a compelling picture for the demonstration of thermal emitters with embedded advanced functionalities through local structuring, such as lenses or holograms.…”

Section: Introductionmentioning

confidence: 99%

Multi-frequency coherent emission from superstructure thermal emitters

Tadjer

Caldwell

et al. 2021

Applied Physics Letters

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Long-range spatial coherence can be induced in thermal emitters by embedding a periodic grating into a material supporting propagating polaritons or dielectric modes. However, the emission angle and frequency cannot be defined simultaneously and uniquely, resulting in emission at unusable angles or frequencies. Here, we explore superstructure gratings (SSGs) to control the spatial and spectral properties of thermal emitters. SSGs have long-range periodicity, but a unit cell that provides tailorable Bragg components to interact with light.These Bragg components allow simultaneous launching of polaritons with different frequencies/wavevectors in a single grating, manifesting as additional spatial and spectral bands upon the emission profile. As the unit cell period approaches the spatial coherence 2 length, the coherence properties of the superstructure will be lost. Whilst the 1D k-space representation of the grating provides insights into the emission, the etch depth of the grating can result in strong polariton-polariton interactions. An emergent effect of these interactions is the creation of polaritonic band gaps, and defect states that can have a well-defined frequency and emission angle. In all, our results show experimentally how even in simple 1D gratings there is significant design flexibility for engineering the profile of thermal emitters, bound by finite coherence length.

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Focused thermal emission from a nanostructured SiC surface

Cited by 49 publications

References 53 publications

Nanophotonic engineering of far-field thermal emitters

Nanophotonic engineering of far-field thermal emitters

The road to atomically thin metasurface optics

Multi-frequency coherent emission from superstructure thermal emitters

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