Plasmonic lens

In nano-optics, a plasmonic lens generally refers to a lens for surface plasmon polaritons (SPPs), i.e. a device that redirects SPPs to converge towards a single focal point. Since SPPs can have very small wavelength, they can converge into a very small and very intense spot, much smaller than the free-space wavelength and the diffraction limit.[1][2]

A simple example of a plasmonic lens is a series of concentric rings on a metal film. Any light that hits the film from free space at normal incidence will get coupled into a SPP (this part works like a grating coupler), and that SPP will be heading towards the center of the circles, which is the focal point.[1][2] Another example is a tapered "dimple".[3]

In 2007, a novel plasmonic lens is proposed by modulating light phase through a metallic film with arrayed nano-slits, which have constant depth but variant widths.[4] The slits transport electromagnetic energy in the form of SPPs in nanometric waveguides and provide desired phase retardations of beam manipulating with variant phase propagation constant. The scientists claim that it is an improvement over other subwavelength imaging techniques, such as "superlenses", where the object and image are confined to the near field.[5]

These devices have been suggested for various applications that take advantage of the small size and high intensity of the SPPs at the focal point. These include photolithography,[2] heat-assisted magnetic recording, microscopy, biophotonics, biological molecule sensors, and solar cells, as well as other applications.[6]

The term "plasmonic lens" is also sometimes used to describe something different: Any free-space lens (i.e., a lens that focuses free-space light, rather than SPPs), that has something to do with plasmonics.[6] These often come up in discussions of superlenses.[6]

References

  1. ↑ 1.0 1.1 Liu, Zhaowei; Steele, Jennifer M.; Srituravanich, Werayut; Pikus, Yuri; Sun, Cheng; Zhang, Xiang (2005). "Focusing Surface Plasmons with a Plasmonic Lens" (free PDF download). Nano Letters 5 (9): 1726–9. Bibcode:2005NanoL...5.1726L. doi:10.1021/nl051013j. PMID 16159213.
  2. ↑ 2.0 2.1 2.2 Srituravanich, Werayut; Pan, Liang; Wang, Yuan; Sun, Cheng; Bogy, David B.; Zhang, Xiang (2008). "Plasmonic lens in the near field for high-speed nanolithography" (Free PDF download). Nature Nanotechnology 3 (12): 733–7. Bibcode:2008NatNa...3..733S. doi:10.1038/nnano.2008.303. PMID 19057593. See also Press release: Denser computer chips possible with plasmonic lenses. UC Berkeley News. 2008-10-22
  3. ↑ "A Plasmonic Dimple Lens for Nanoscale Focusing of Light" doi: 10.1021/nl9016368
  4. ↑ Xu, T.; Du, C.; Wang, C.; Luo, X.G. (13 Nov 2007). "Subwavelength imaging by metallic slab lens with nanoslits". Applied Physics Letters 91: 201501. doi:10.1063/1.2811711.
  5. ↑ Dumé, Belle. "Nano-lens moves on". IOP group. Retrieved Mar 10, 2008.
  6. ↑ 6.0 6.1 6.2 Published: October 24, 2012 under CC BY 3.0 license Fu, Yongqi; Wang, Jun; Zhang, Daohua (2012). "Plasmonics - Principles and Applications" (free PDF download (Google scholar)). doi:10.5772/50029. ISBN 978-953-51-0797-2. |chapter= ignored (help)Published: October 24, 2012 under CC BY 3.0 license

Further reading