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Electromagnetic field radiated by a point emitter on a graphene sheet

Electromagnetic field radiated by a point emitter on a graphene sheet. In collaboration with: Luis Mart ín-Moreno , F. J. Garc í a-Vidal ( UAM, Madrid ). Alexey Nikitin Instituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-CSIC). website: alexeynik.com.

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Electromagnetic field radiated by a point emitter on a graphene sheet

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  1. Electromagnetic field radiated by a point emitter on a graphene sheet In collaboration with: Luis Martín-Moreno, F. J. García-Vidal (UAM, Madrid) Alexey Nikitin Instituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-CSIC) website:alexeynik.com Zaragoza, 03/02/2011

  2. Outline of the presentation • Why graphene? Unusual properties • Surface EM waves in graphene • A point source: the fundamental problem • Radiation patterns: surface plasmons and free-space fields • Possible applications

  3. Why graphene? Unusual properties

  4. Why graphene? Unusual optical properties Optical solutions: possible future of Electronics? Thin metallic optical interconnectors Graphene optical interconnectors

  5. Why graphene? Unusual optical properties Atomic structure and electronic properties • One atomic layer-thick • Zero mass of electrons • High electron mobility • Pronounced response to external voltage Graphene transistors and integrated circuits Y.-M. Lin et al. (IBM), Science 327, 662 (2010) H. B. Heersche et al., Nature 446, 56 (2007) supercurrent transistor cutoff frequency of 100 GHz for a gate length of 240 nm

  6. Why graphene? Unusual optical properties Optical properties • It absorbs of white light • Conductivity is sensible to external fields • Saturable absorption • Could be made luminescent • Supports surface electromagnetic waves Extremely thin, but seen with the naked eye Graphene-based optoelectronics Solar cell LED Flexible smart window F. Bonaccorso et al., Nature Phot. 4, 611 (2010)

  7. Surface EM waves in graphene

  8. Surface EM waves in graphene Surface plasmons (SPs) in metallic surafces Light cone SPs q SP q q q W. L. Barnes et al., Nature 424, 824 (2003)

  9. Surface EM waves in graphene Conductivity of graphene

  10. Surface EM waves in graphene Surface waves in graphene

  11. Surface EM waves in graphene Graphene metamaterials and Transformation Optics Ashkan Vakil and Nader Engheta, arXiv: optics/1101.3585 2D graphene plasmonic prism Spatial varying voltage Transformation Optics devices 2D graphene plasmonic waveguide

  12. A point source: the fundamental problem

  13. A point source: the fundamental problem Possible sources for local excitation molecule Josephson qubit quantum dot

  14. A point source: the fundamental problem Electric dipole

  15. A point source: the fundamental problem Computational difficulties: asymptotic approach oscillating factor branch cut branch cut pole pole graphene Radiowave propagation problems L. P. Felsen and N. Marcuvitz, Radiation and Scattering of Waves (IEEE Press, Piscataway, NJ, 1994)

  16. Radiation patterns: SPs and free-space fields Density of electromagnetic states

  17. Radiation patterns: surface plasmonsand free-space fields

  18. Radiation patterns: SPs and free-space fields Vertical dipole SP characteristics:

  19. Radiation patterns: SPs and free-space fields Vertical dipole SP characteristics:

  20. Radiation patterns: SPs and free-space fields Vertical dipole No SP excited SP characteristics: No SP excited

  21. Radiation patterns: SPs and free-space fields Horizontal dipole • SP characteristics: • long propagation length • wavelength close to the vacuum one

  22. Radiation patterns: SPs and free-space fields Horizontal dipole • SP characteristics: • medium propagation length (of order of several wavelengths) • wavelength is quite less than the vacuum one

  23. Radiation patterns: SPs and free-space fields Horizontal dipole No SP excited

  24. Possible applications

  25. Possible applications EM fields created by apertures in graphene Qubits coupling through graphene SPs waveguides A. Gonzalez-Tudela et al., PRL 106, 020501 (2011) • Vakil et al., • arXiv: optics/1101.3585 A. Yu. Nikitin et al., PRL 105, 073902 (2010)

  26. Conclusions Conclusions • In spite of being very transparent (97.7%), graphene can trap electromagnetic fields on its surface. • The fields excited by point sources (like molecules or quantum dots) can reach huge values. • The shape of the excited fields can be controlled by voltage, wavelength or temperature. • Found properties of graphene are promising for using it in different photonic or quantum circuits.

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