Electromagnetic metasurface

An electromagnetic metasurface refers to a kind of artificial sheet material with sub-wavelength thickness. Metasurfaces can be either structured or unstructured with subwavelength-scaled patterns in the horizontal dimensions.[1]

In electromagnetic theory, metasurfaces modulate the behaviors of electromagnetic waves through specific boundary conditions, rather than constitutive parameters in three dimensional (3D) space, which is commonly exploited in natural materials and metamaterials. Metasurfaces may also refer to the two-dimensional counterparts of metamaterials.[2]

Definitions

Metasurfaces have been defined in several ways by researchers.

1, “An alternative approach that has gained increasing attention in recent years deals with one- and two-dimensional (1D and 2D) plasmonic arrays with subwavelength periodicity, also known as metasurfaces. Due to their negligible thickness compared to the wavelength of operation, metasurfaces can (near resonances of unit cell constituents) be considered as an interface of discontinuity enforcing an abrupt change in both the amplitude and phase of the impinging light”.[3]

2, “Our results can be understood using the concept of a metasurface, a periodic array of scattering elements whose dimensions and periods are small compared with the operating wavelength”.[4]

3, “Metasurfaces based on thin films”. A highly absorbing ultrathin film on a substrate can be also considered as a metasurface, with properties not occurring in natural materials.[1] Following this definition, the thin metallic films such as that in superlens are also early type of metasurfaces.[5]

History

The research of electromagnetic metasurfaces has a long history. Early in 1902, Robert W. Wood found that the reflection spectra of subwavelength metallic grating had dark areas. This unusual phenomenon was named Wood’s anomaly and led to the discovery of the surface plasmon polariton (SPP),[6] a particular electromagnetic wave excited at metal surfaces. Subsequently, another important phenomenon, the Levi-Civita relation,[7] was introduced, which states that a subwavelength-thick film can result in a dramatic change in electromagnetic boundary conditions.

Generally speaking, metasurfaces could include some traditional concepts in the microwave spectrum such as frequency selective surfaces (FSS), impedance sheets and even Ohmic sheets. In the microwave regime, the thickness of these metasurfaces can be much smaller than the wavelength of operation (for example, 1/1000 of the wavelength), since the skin depth could be extremely small for highly conductive metals. Recently, some novel phenomena such as ultra-broadband coherent perfect absorption were demonstrated. The results showed that a 0.3 nm thick film could absorb all electromagnetic waves across the RF, microwave, and terahertz frequencies.[8][9][10]

In optical applications, an anti-reflective coating could also be regarded as a simple metasurface, as first observed by Lord Rayleigh.

In recent years, several new metasurfaces have been developed, including Plasmonic metasurfaces,[2][3][11] metasurfaces based on geometric phases,[12][13] and metasurfaces based on impedance sheets.[14][15]

Applications

One the most important applications of metasurfaces is to control a wavefront of electromagnetic waves by imparting local, gradient phase shifts to the incoming waves, which leads to a generalization of the ancient laws of reflection and refraction.[12] In this way, a metasurface can be used as a planar lens,[16] vortex generator,[17] beam deflector, axicon and so on.[13][18]

Besides the gradient metasurface lenses, metasurface-based superlenses offer another degree of control of the wavefront by using evanescent waves. With surface plasmons in the ultrathin metallic layers, perfect imaging and super-resolution lithography could be possible, which breaks the common assumption that all optical lens systems are limited by diffraction, a phenomenon called the diffraction limit.[19][20]

Another promising application is in the field of stealth technology. A target's radar cross-section (RCS) has conventionally been reduced by either radiation-absorbent material (RAM) or by purpose shaping of the targets such that the scattered energy can be redirected away from the source. Unfortunately, RAMs have narrow frequency-band functionality, and purpose shaping limits the aerodynamic performance of the target. Metasurfaces have been synthesized that redirect scattered energy away from the source using either array theory[21][22] or the generalized Snell's law.[23][24] This has led to aerodynamically favorable shapes for the targets with reduced RCS.

In addition, metasurfaces are also applied in electromagnetic absorbers, polarization converters, and spectrum filters.

References

  1. 1 2 Yu, Nanfang; Capasso, Federico (2014). "Flat optics with designer metasurfaces". Nat. Mater. 13: 139–150. Bibcode:2014NatMa..13..139Y. doi:10.1038/nmat3839.
  2. 1 2 Zeng, S.; et al. (2015). "Graphene-gold metasurface architectures for ultrasensitive plasmonic biosensing". Advanced Materials. 27: 6163–6169. doi:10.1002/adma.201501754.
  3. 1 2 Pors, Anders; Bozhevolnyi, Sergey I. (2013). "Plasmonic metasurfaces for efficient phase control in reflection". Optics Express. 21: 27438. Bibcode:2013OExpr..2127438P. doi:10.1364/OE.21.027438.
  4. ↑ Li, Ping-Chun; Zhao, Yang; Alu, Andrea; Yu, Edward T. (2011). "Experimental realization and modeling of a subwavelength frequency-selective plasmonic metasurface". Appl. Phys. Lett. 99: 221106. Bibcode:2011ApPhL..99c1106B. doi:10.1063/1.3614557.
  5. ↑ Pendry, J. B. (2000). "Negative Refraction Makes a Perfect Lens" (PDF). Physical Review Letters. 85 (18): 3966–9. Bibcode:2000PhRvL..85.3966P. doi:10.1103/PhysRevLett.85.3966. PMID 11041972.
  6. ↑ Wood, R. W. (1902). "On a remarkable case of uneven distribution of light in a diffraction grating spectrum". Proc. Phys. Soc. Lond. 18: 269–275. Bibcode:1902PPSL...18..269W. doi:10.1088/1478-7814/18/1/325.
  7. ↑ Senior, T. (1981). "Approximate boundary conditions". IEEE Trans. Antennas Propag. 29: 826–829. Bibcode:1981ITAP...29..826S. doi:10.1109/tap.1981.1142657.
  8. ↑ Pu, M.; et al. (17 January 2012). "Ultrathin broadband nearly perfect absorber with symmetrical coherent illumination". Optics Express. 20 (3): 2246–2254. Bibcode:2012OExpr..20.2246P. doi:10.1364/oe.20.002246.
  9. ↑ Li, S.; et al. "Broadband Perfect Absorption of Ultrathin Conductive Films with Coherent Illumination: Super Performance of Electromagnetic Absorption". Physical Review B. 91. arXiv:1406.1847. Bibcode:2015PhRvB..91v0301L. doi:10.1103/PhysRevB.91.220301.
  10. ↑ Taghvaee, H.R.; et al. (2017). "Circuit modeling of graphene absorber in terahertz band". Optics Communications. 383: 11–16. doi:10.1016/j.optcom.2016.08.059.
  11. ↑ Verslegers, Lieven; Fan, Shanhui (2009). "Planar Lenses Based on Nanoscale Slit Arrays in a Metallic Film". Nano Lett. 9: 235–238. Bibcode:2009NanoL...9..235V. doi:10.1021/nl802830y.
  12. 1 2 Yu, Nanfang; Genevet, Patrice; Kats, Mikhail A.; Aieta, Francesco; Tetienne, Jean-Philippe; Capasso, Federico; Gaburro, Zeno (2011). "Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction". Science. 334: 333–337. Bibcode:2011Sci...334..333Y. doi:10.1126/science.1210713. PMID 21885733.
  13. 1 2 Lin, Dianmin; Fan, Pengyu; Hasman, Erez; Brongersma, Mark L. (2014). "Dielectric gradient metasurface optical elements". Science. 345: 298–302. Bibcode:2014Sci...345..298L. doi:10.1126/science.1253213. PMID 25035488.
  14. ↑ Pfeiffer, Carl; Grbic, Anthony (2013). "Metamaterial Huygens' Surfaces: Tailoring Wave Fronts with Reflectionless Sheets". Phys. Rev. Lett. 110: 197401. arXiv:1206.0852. Bibcode:2013PhRvL.110b7401W. doi:10.1103/PhysRevLett.110.027401.
  15. ↑ Felbacq, Didier (2015). "Impedance operator description of a metasurface". Mathematical Problems in Engineering. 2015: 473079. doi:10.1103/10.1155/2015/473079.
  16. ↑ Aieta, Francesco; Genevet, Patrice; Kats, Mikhail; Yu, Nanfang; Blanchard, Romain; Gaburro, Zeno; Capasso, Federico (2012). "Aberration-free ultra-thin flat lenses and axicons at telecom wavelengths based on plasmonic metasurfaces". Nano Letters. 12: 4932–6. arXiv:1207.2194. Bibcode:2012NanoL..12.4932A. doi:10.1021/nl302516v. PMID 22894542.
  17. ↑ Genevet, Patrice; Yu, Nanfang; Aieta, Francesco; Lin, Jiao; Kats, Mikhail; Blanchard, Romain; Scully, Marlan; Gaburro, Zeno; Capasso, Federico (2012). "Ultra-thin plasmonic optical vortex plate based on phase discontinuities". Applied Physics Letters. 100: 013101. Bibcode:2012ApPhL.100a3101G. doi:10.1063/1.3673334.
  18. ↑ Xu, T.; et al. (2008). "Plasmonic deflector". Opt. Express. 16: 4753. Bibcode:2008OExpr..16.4753X. doi:10.1364/oe.16.004753.
  19. ↑ Luo, Xiangang; Ishihara, Teruya (2004). "Surface plasmon resonant interference nanolithography technique". Appl. Phys. Lett. 84: 4780. Bibcode:2004ApPhL..84.4780L. doi:10.1063/1.1760221.
  20. ↑ Fang, Nicholas; Lee, Hyesog; Sun, Cheng; Zhang, Xiang (2005). "Sub-Diffraction-Limited Optical Imaging with a Silver Superlens". Science. 308: 534–7. Bibcode:2005Sci...308..534F. doi:10.1126/science.1108759. PMID 15845849.
  21. ↑ A. Y. Modi; C. A. Balanis; C. R. Birtcher; H. Shaman, "Novel Design of Ultrabroadband Radar Cross Section Reduction Surfaces using Artificial Magnetic Conductors," in IEEE Transactions on Antennas and Propagation, vol.65, no.10, pp. 5406-5417, Oct. 2017. doi: 10.1109/TAP.2017.2734069
  22. ↑ M. E. de Cos, Y. Alvarez-Lopez, and F. Las Heras Andres, "A novel approach for RCS reduction using a combination of artificial magnetic conductors," Progress In Electromagnetics Research, Vol. 107, 147-159, 2010. doi:10.2528/PIER10060402
  23. ↑ Appl. Phys. Lett. 104, 221110 (2014). doi: 10.1063/1.4881935
  24. ↑ Yu, Nanfang; Genevet, Patrice; Kats, Mikhail A.; Aieta, Francesco; Tetienne, Jean-Philippe; Capasso, Federico; Gaburro, Zeno (October 2011). "Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction". Science. 334 (6054): 333. Bibcode:2011Sci...334..333Y. doi:10.1126/science.1210713. PMID 21885733.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.