- Metamaterial absorber
A metamaterial absorber manipulates the loss components of the complex effective parameters, permittivity and magnetic permeability of metamaterials, to create a material with particularly high absorption. Loss is noted in applications of negative refractive index (photonic metamaterials, antenna systems metamaterials) or transformation optics (metamaterial cloaking, celestial mechanics), but is typically undesired in these applications.
Complex permittivity and permeability are derived from metamaterials using the effective medium approach. As effective media, metamaterials can be characterized with complex ε(w) = ε1 + iε2 for effective permittivity and µ(w) = µ1 + i µ2 for effective permeability. Complex values of permittivity and permeability typically correspond to attenuation in a medium. Most of the work in metamaterials is focused on the real parts of these parameters, which relate to wave propagation rather than attenuation. The loss (imaginary) components are small in comparison to the real parts and are often neglected in such cases.
However, the loss terms (ε2 and µ2) can also be engineered to create high attenuation and correspondingly large absorption. By independently manipulating resonances in ε and µ, it is possible to absorb both the incident electric and magnetic field. Additionally, a metamaterial can be impedance-matched to free space by engineering its permittivity and permeability, minimizing reflectivity. Thus, it becomes a highly capable absorber.
This approach can be used to create thin absorbers. Typical conventional absorbers are thick compared to wavelengths of interest, which is a problem in many applications. Since metamaterials are characterized based on their subwavelength nature, they can be used to create effective, thin absorbers. This is not limited to electromagnetic absorption, either.
- ^ a b Landy, N. I. et al; Sajuyigbe, S.; Mock, J.; Smith, D.; Padilla, W. (2008-05-21). "Perfect Metamaterial Absorber". Phys. Rev. Lett 100: 207402 (2008) [4 pages]. Bibcode 2008PhRvL.100t7402L. doi:10.1103/PhysRevLett.100.207402. PMID 18518577. http://www2.bc.edu/~padillaw/PDF/PRL_100_207402_2008.pdf. Retrieved 2010-01-22.
- ^ a b Tao, Hu et al; Landy, Nathan I.; Bingham, Christopher M.; Zhang, Xin; Averitt, Richard D.; Padilla, Willie J. (2008-05-12). "A metamaterial absorber for the terahertz regime: Design, fabrication and characterization" (Free PDF download). Optics Express 16: pp. 7181–7188. Bibcode 2008OExpr..16.7181T. doi:10.1364/OE.16.007181. PMID 18545422. http://www2.bc.edu/~padillaw/PDF/Opt_Exp_16_7181_2008.pdf. Retrieved 2010-01-22.
- ^ a b Yang, Z. et al; Dai, H. M.; Chan, N. H.; Ma, G. C.; Sheng, Ping (2010). "Acoustic metamaterial panels for sound attenuation in the 50–1000 Hz regime". Appl. Phys. Lett. 96: 041906 [3 pages]. Bibcode 2010ApPhL..96d1906Y. doi:10.1063/1.3299007.
Wikimedia Foundation. 2010.