Research Papers

Manipulation of Thermal Emission by Use of Micro and Nanoscale Structures

[+] Author and Article Information
Erez Hasman, Vladimir Kleiner, Nir Dahan, Yuri Gorodetski, Kobi Frischwasser, Igal Balin

 Micro and Nanooptics Laboratory, Faculty of Mechanical Engineering, Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology, Haifa 32000, Israelmehasman@technion.ac.il

J. Heat Transfer 134(3), 031023 (Jan 20, 2012) (7 pages) doi:10.1115/1.4005160 History: Received November 03, 2010; Revised January 20, 2011; Published January 20, 2012; Online January 20, 2012

In high temperature and vacuum applications, for which heat transfer is predominantly by radiation, the material’s surface texture is of substantial importance. Several micro and nanostructures designs have been proposed to enhance a material’s emissivity and its radiative coherence. Control of thermal emission is of crucial concern in the design of infrared sources, in electronic chip coolants, in high-efficiency photovoltaic cells, and in solar energy conversion. In this review paper, we present microscale and nanoscale structures supporting surface waves for obtaining polarization manipulation of thermal emission, extraordinary coherent thermal radiation, bandgap in the spectral emission, spin symmetry breaking of coupled thermal antenna array, and a broadband infrared absorption.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

(a) Measured (solid) and calculated (dashed) relative emissivity spectrum of the grating for TM, TE polarization, and without a polarizer in normal observation direction, with grating parameters: period 2 μm, fill factor 0.3, and depth 0.8 μm. The element was heated to a temperature of 873 K. The inset shows a scanning electron microscope (SEM) image of the grating. (b) Measured and calculated (solid) relative emissivity as a function of observation angle. (c) SEM images of the spiral subwavelength elements with polarization order numbers m = 1, 2, 3, and 4. (d) Thermal emission images emerging from the SiO2 spiral elements captured through a polarizer and (e) without a polarizer. The lines indicate the local TM polarization orientation measured in the near field. The elements were uniformly heated to a temperature of 353 K.

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Figure 2

(a) SEM image of CRC structure upon SiC, with period of 11.6 μm, fill factor 0.56, and cavity depth of 4.6 μm. (b) Theoretical emissivity distribution as a function of frequency and observation angle θ. (c) Calculated (orange) and experimental (purple) directional emissivity at the peak frequency and (d) spectral emissivity in the normal direction. (e) Calculated electric field distribution in the x-z plane, |Ex | and (f) |Ez |.

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Figure 3

(a) SEM image of realized BBS with period Λ = 11.2 μm, depth h = 510 nm, and amplitude ratio R = 1. (b) Measured (blue dots) and calculated (black solid curves) spectral emissivity at normal incidence (k = 0). One can see the bandgaps for several values of R; dashed red lines indicate locations of the bandgaps. Measured dispersion of thermal emission from binary coupler grating (c), and BBSs with R = 2/3 (d), R = 4/5 (e), and R = 1 (f). RCWA calculations are depicted by solid white lines.

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Figure 4

(a) top: SEM image of the homogeneous rod array (1.2 μm × 4.8 μm, Λ=11.6μm, depth of 1 μm on a SiC); bottom: SEM of the rod array rotating along the x-axis with a period a=6Λ (Ω=π/a); inset—SEM image of a single rod. (b) The measured emission dispersion of the homogeneous rod array. Dashed lines highlight the dispersion of the slow and the fast modes. (c) Measured dispersion of the rotating rod array. Dashed/dotted black lines indicate the split slow modes. (d) Spin-projected dispersion of the rotating rod array, obtained by S3 measurement. Dashed/dotted lines highlight the dispersion of the spin-split slow mode (red/blue color corresponds to a positive/negative spin projection, respectively). The observed dispersion shift is Δk=σΩ.

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Figure 5

(a) Concept of a resonant absorber using a metallic subwavelength structure as a metamaterial absorbing layer including a microscope image of the measured NiCr structure with Λ = 4 μm, q = 0.5, and h = 30 nm on a GaAs. (b) Simulated (closed circles), theoretical (solid curve) and measured (cross point) of n·k as a function of area fill factor, q2 , for the metallic NiCr plates structure depicted in the upper right inset at 11 μm wavelength. Dashed curve represents effective medium approximation for a structure composed of metallic NiCr spheres. Open circles represent numerical calculation of a NiCr structure (0.1 μm period with 30 nm thickness). (c) Calculated absorption of a resonator configuration as a function of incident wavelength (at normal incident angle) for: NiCr subwavelength structure depicted in part (a) (solid curve); and 30 nm (dashed curve) of uniform NiCr thin film.




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