Browsing by Author "Wang, Liping"

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Near-field radiative heat transfer between nanowire-based dual uniaxial magneto-dielectric metamaterials
(2020-09-01)
Chang, Jui-Yung
;
Sabbaghi, Payam
;
Wang, Liping
;
機械工程學系
;
Department of Mechanical Engineering
Over past several years, much attention has been paid on near-field radiation with super-Planckian heat flux due to resonant coupling of surface polaritons and non-resonant hyperbolic modes but mainly with non-magnetic materials. With nanowire-based magneto-dielectric metamaterials, this work theoretically investigates the near-field radiative heat transfer associated with both uniaxial magnetic and electric responses. Maxwell-Garnett effective medium theory is used to obtain the dual uniaxial effective permeability and permittivity of the magneto-dielectric metamaterials. With the fluctuational electrodynamics, multiple resonant and non-resonant modes associated with both magnetic and electric responses that spectrally enhance the radiative heat transfer, such as magnetic and electric hyperbolic modes, magnetic and electric surface polaritons, mu- and epsilon-near-pole modes, are identified and elucidated at different wave polarizations. Effects of filling ratio, magnetic and electric scattering rates, and vacuum gap distance are also studied, and it is found that the spectral and total heat fluxes of s-polarized waves, which are usually neglected for non-magnetic materials, are much enhanced and comparable with that of p-polarized waves. The results here will deepen the fundamental understanding in magneto-dielectric metamaterials and facilitate their applications in the area of near-field thermal radiation. (C) 2020 Elsevier Ltd. All rights reserved.
Retrieval of Uniaxial Permittivity and Permeability for the Study of Near-Field Radiative Transport Between Metallic Nanowire Arrays
(2020-07-01)
Chang, Jui-Yung
;
Sabbaghi, Payam
;
Weng, Yu-Shao
;
Chen, Yu-Bin
;
Wang, Liping
Recently metamaterials made of periodic nanowire arrays, multilayers, and grating structures have been studied for near-field thermal radiation with enhanced coupling of evanescent waves due to surface plasmon/phonon polariton, hyperbolic mode, epsilon-near-zero and epsilon-near-pole (ENP) modes, guided mode, and wave interference. In this work, both effective uniaxial electric permittivity and magnetic permeability of a nanowire-based metamaterial are retrieved theoretically through the far-field radiative properties obtained by finite difference time-domain (FDTD) simulations. The artificial magnetic response of metamaterials, which cannot be obtained by traditional effective medium theory (EMT) based on electric permittivity of constitutes only, is successfully captured by the nonunity magnetic permeability, whose resonant frequency is verified by an inductor-capacitor model. By incorporating the retrieved electric permittivity and magnetic permeability into fluctuational electrodynamics with multilayer uniaxial wave optics, the near-field radiative heat transfer between the metallic nanowire arrays is theoretically studied and spectral near-field heat enhancements are found for both transverse electric and magnetic waves due to artificial magnetic resonances. The understanding and insights obtained here will facilitate the application of metamaterials in near-field radiative transfer.