Nanophotonics

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Nanophotonics or Nano-optics is the study of the behavior of light on the nanometer scale, and of the interaction of nanometer-scale objects with light. It is a branch of optics, optical engineering, and nanotechnology. It often (but not exclusively) involves metallic components, which can transport and focus light via surface plasmon polaritons.

The term "nano-optics", just like the term "optics", usually concerns ultraviolet, visible, and near-infrared light (free-space wavelength around 300-1200 nanometers).

Background[edit]

Normal optical components, like lenses and microscopes, generally cannot normally focus light to nanometer (deep subwavelength) scales, because of the diffraction limit (Rayleigh criterion). Nevertheless, it is possible to squeeze light into a nanometer scale using other techniques like, for example, surface plasmons, localized surface plasmons around nanoscale metal objects, and the nanoscale apertures and nanoscale sharp tips used in near-field scanning optical microscopy (NSOM) and photoassisted scanning tunnelling microscopy.[1]

Motivations[edit]

Nanophotonics researchers pursue a very wide variety of goals, in fields ranging from biochemistry to electrical engineering. A few of these goals are summarized below.

Optoelectronics and microelectronics[edit]

Solar cells[edit]

Spectroscopy[edit]

Microscopy[edit]

Principles[edit]

Plasmons and metal optics[edit]

Main articles: Plasmon and Surface plasmon

Metals are an effective way to confine light to far below the wavelength. This was originally used in radio and microwave engineering, where metal antennas and waveguides may be hundreds of times smaller than the free-space wavelength. For a similar reason, visible light can be confined to the nano-scale via nano-sized metal structures, such as nano-sized structures, tips, gaps, etc. This effect is somewhat analogous to a lightning rod, where the field concentrates at the tip.

This effect is fundamentally based on the fact that the permittivity of the metal is very large and negative. At very high frequencies (near and above the plasma frequency, usually ultraviolet), the permittivity of a metal is not so large, and the metal stops being useful for concentrating fields.

Many nano-optics designs look like common microwave or radiowave circuits, but shrunk down by a factor of 100,000 or more. After all, radiowaves, microwaves, and visible light are all electromagnetic radiation; they differ only in frequency. So other things equal, a microwave circuit shrunk down by a factor of 100,000 will behave the same way but at 100,000 times higher frequency. For example, researchers have made nano-optical Yagi-Uda antennas following essentially the same design as used for radio Yagi-Uda antennas.[12] That said, there are a number of very important differences between nano-optics and scaled-down microwave circuits. For example, at optical frequency, metals behave much less like ideal conductors, and also exhibit interesting plasmon-related effects like kinetic inductance and surface plasmon resonance. Likewise, optical fields interact with semiconductors in a fundamentally different way than microwaves do.

Near-field optics[edit]

If you take the Fourier transform of an object, it consists of different spatial frequencies. The higher frequencies correspond to the very fine features and sharp edges.

When light is emitted by such an object, the light with very high spatial frequency forms an evanescent wave, which only exists in the near field (very close to the object, within a wavelength or two) and disappears in the far field. This is the origin of the diffraction limit, which says that when a lens images an object, the subwavelength information is blurred out.

Nano-photonics is primarily concerned with the near-field evanescent waves. For example, a superlens (mentioned above) would prevent the decay of the evanescent wave, allowing higher-resolution imaging.

Metamaterials[edit]

Main article: Metamaterial

Metamaterials are artificial materials engineered to have properties that may not be found in nature. They are created by fabricating an array of structures much smaller than a wavelength. The small (nano) size of the structures is important: That way, light interacts with them as if they made up a uniform, continuous medium, rather than scattering off the individual structures.

References[edit]

  1. ^ Hewakuruppu, Y., et al., Plasmonic “ pump – probe ” method to study semi-transparent nanofluids, Applied Optics, 52(24):6041-6050
  2. ^ Assefa, Solomon; Xia, Fengnian; Vlasov, Yurii A. (2010). "Reinventing germanium avalanche photodetector for nanophotonic on-chip optical interconnects". Nature 464 (7285): 80–4. Bibcode:2010Natur.464...80A. doi:10.1038/nature08813. PMID 20203606. 
  3. ^ a b "Research Discovery By Ethiopian Scientist At IBM at Tadias Magazine". Tadias.com. Retrieved 2010-03-15. 
  4. ^ "Avalanche photodetector breaks speed record". physicsworld.com. Retrieved 2010-03-15. 
  5. ^ Themistoklis P. H. Sidiropoulos, Robert Röder, Sebastian Geburt, Ortwin Hess, Stefan A. Maier, Carsten Ronning, Rupert F. Oulton (2014). "Ultrafast plasmonic nanowire lasers near the surface plasmon frequency". Nature Physics. doi:10.1038/nphys3103.  Press release
  6. ^ Hand, Aaron. "High-Index Lenses Push Immersion Beyond 32 nm". 
  7. ^ Liang Pan et al. (2011). "Maskless Plasmonic Lithography at 22 nm Resolution". Scientific Reports. doi:10.1038/srep00175. 
  8. ^ "IBM Research | IBM Research | Silicon Integrated Nanophotonics". Domino.research.ibm.com. 2010-03-04. Retrieved 2010-03-15. 
  9. ^ Vivian E. Ferry, Jeremy N. Munday, Harry A. Atwater (2010-11). "Design Considerations for Plasmonic Photovoltaics". Advanced Materials 22 (43): 4794–4808. doi:10.1002/adma.201000488. 
  10. ^ "Enhancing single-molecule fluorescence with nanophotonics", DOI: 10.1016/j.febslet.2014.06.016
  11. ^ R. Zhang, Y. Zhang, Z. C. Dong, S. Jiang, C. Zhang, L. G. Chen, L. Zhang, Y. Liao, J. Aizpurua, Y. Luo, J. L. Yang, J. G. Hou (6 June 2013). "Chemical mapping of a single molecule by plasmon-enhanced Raman scattering". Nature 498: 82–86. doi:10.1038/nature12151. 
  12. ^ Daniel Dregely, Richard Taubert, Jens Dorfmüller, Ralf Vogelgesang, Klaus Kern, Harald Giessen. "3D optical Yagi–Uda nanoantenna array". Nature Communications 2 (267). doi:10.1038/ncomms1268. 

External links[edit]

Photonics journals[edit]