Abstract
We report the design of dielectric-filled anti-reflection coated (ARC) two-dimensional (2D) metallic photonic crystals (MPhCs) capable of omnidirectional, polarization insensitive, wavelength selective emission/absorption. Using non-linear global optimization methods, optimized hafnium oxide (HfO2)-filled ARC 2D Tantalum (Ta) PhC designs exhibiting up to 26% improvement in emittance/absorptance at wavelengths λ below a cutoff wavelength λc over the unfilled 2D TaPhCs are demonstrated. The optimized designs possess high hemispherically average emittance/absorptance εH of 0.86 at λ < λc and low εH of 0.12 at λ > λc.
Highlights
Occurring materials usually exhibit thermal emission profiles that are broadband, and have a magnitude far weaker compared to the ideal blackbody
For instance as a selective emitter in TPV energy conversion systems, it is more advantageous to possess broader emission bandwidth such that high emittance is retained at wavelengths λ smaller than a particular cutoff wavelength λcut, while maintaining ultra-low emittance at λ > λcut over all exitance angles and polarizations
Up to 15% relative improvement is seen in Jelec with the optimized HfO2-filled anti-reflection coated (ARC) 2D Ta PhC compared to the unfilled 2D Ta PhC due to 26% relative improvement in hemispherically averaged emittance at λ < λcut
Summary
Occurring materials usually exhibit thermal emission profiles that are broadband, and have a magnitude far weaker compared to the ideal blackbody This is inefficient for many applications, for instance as an infrared source in sensing applications,[1,2] as an emitter in thermophotovoltaic (TPV) energy conversion,[3,4] and as a solar absorber.[5,6] For many of these applications, it is desirable to accurately control thermal radiation such that thermal emission occurs only in certain wavelength ranges over an optimum angular spread. For instance as a selective emitter in TPV energy conversion systems, it is more advantageous to possess broader emission bandwidth such that high emittance is retained at wavelengths λ smaller than a particular cutoff wavelength λcut, while maintaining ultra-low emittance at λ > λcut over all exitance angles and polarizations In this respect, metamaterial designs based on metal dielectric stacks[9] and 2D metallic pyramid arrays[15] show great promise. We present a simpler approach based on dielectric-filled anti-reflection coated (ARC) 2D metallic photonic crystals (MPhCs) to obtain omnidirectional polarization insensitive wavelength selective thermal emission
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