Extraordinary optical transmission
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Extraordinary optical transmission (EOT) is an optical phenomenon that happens in slits that are narrower than the wavelength of the light. Generally when light falls on such a slit, it emerges having been diffracted isotropically, ie it scatters in all directions evenly. However, if instead the slit is surrounded by highly patterned grooves, a highly directional beam emerges instead of the diffracted & isotropic beam. This is called an Extraordinary Optical Transmission.
This phenomenon is attributed to the presence of surface plasmon resonances and constructive interference. A surface plasmon (SP) is a collective excitation of the electrons at the junction between a conductor and an insulator and is one of a series of interactions between light and a metal surface called Plasmonics.
Currently, there is experimental evidence of EOT out of the optical range [2]. Analytical approaches also predict EOT on perforated plates with a perfect conductor model [3,4]. Therefore, it is now well-established that the phenomenon is mainly dependent on diffraction and that it can be attributed to a self-resonance of the hole array structure. Holes can somewhat emulate plasmons at other regions of the Electromagnetic spectrum where they do not exist [5]. Then, the plasmonic contribution is a very particular peculiarity of the EOT resonance and should not be taken as the main contribution to the phenomenon.
[edit] Applications
EOT is expected to play an important role in the creation of components of 'photonic' circuits. (Photonic circuits are analogous to electronic circuits.)
One of the most ground-breaking results linked to EOT is the possibility to implement a Left-Handed Metamaterial (LHM) by simply stacking hole arrays, as demonstrated in [6].
[edit] References
[1] Ebbesen, T. W.; Ghaemi, H. F.; Thio, Tineke; Grupp, D. E.; Lezec, H. J, "Extraordinary Optical Transmission through Sub-wavelength Hole Arrays", APS 1998, http://adsabs.harvard.edu/abs/1998APS..MAR.S1511E
[2] M. Beruete, M. Sorolla, I. Campillo, J.S. Dolado, L. Martín-Moreno, J. Bravo-Abad, and F. J. García-Vidal, “Enhanced Millimeter Wave Transmission Through Quasioptical Subwavelength Perforated Plates”, IEEE Trans. Antennas and Propagation, Vol. 53, No. 6, pp. 1897-1903, June 2005.
[3] C.C. Chen, "Transmission through a Conducting Screen Perforated Periodically with Apertures", IEEE Trans. Microw. Theory and Tech., Vol. 18, No. 9, pp. 627-632, Sep. 1970
[4] L. Martín-Moreno, F. J. García-Vidal, H. J. Lezec, K. M. Pellerin, T. Thio, J. B. Pendry, and T.W. Ebbesen, “Theory of Extraordinary Optical Transmission through Subwavelength Hole Arrays”, Phys. Rev. Lett., Vol. 86, pp. 1114-1117, (2001).
[5] J. B. Pendry, L. Martín-Moreno, and F. J. García-Vidal, “Mimicking surface plasmons with structured surfaces,” Science, Vol. 305, pp. 847 - 848, 6 August 2004.
[6] M. Beruete, M. Sorolla, and I. Campillo,”Left-Handed Extraordinary Optical Transmission through a Photonic Crystal of Subwavelength Hole Arrays”, Optics Express, Vol. 14, No. 12, pp. 5445-5455, (12 June 2006). http://www.opticsexpress.org/abstract.cfm?id=90303
