Electromagnetic field radiated by a point emitter on a graphene sheet
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Transcript of Electromagnetic field radiated by a point emitter on a graphene sheet
Electromagnetic field radiated by a point emitter on a graphene sheet
Alexey NikitinInstituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-CSIC)
Zaragoza, 03/02/2011
In collaboration with:Luis Martín-Moreno, F. J. García-Vidal (UAM, Madrid)
website: alexeynik.com
Outline of the presentation
Why graphene? Unusual properties
Surface EM waves in graphene
Radiation patterns: surface plasmons and free-space fields
A point source: the fundamental problem
Possible applications
Why graphene? Unusual properties
Why graphene? Unusual optical properties
Optical solutions: possible future of Electronics?
Thin metallic optical interconnectors
Graphene optical interconnectors
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
H. B. Heersche et al., Nature 446, 56 (2007)
Y.-M. Lin et al. (IBM), Science 327, 662 (2010)
cutoff frequency of 100 GHz for a gate length of 240 nm supercurrent transistor
Why graphene? Unusual optical properties
Optical properties
Extremely thin, but seen with the naked eye
• It absorbs of white light
• Conductivity is sensible to external fields
• Saturable absorption
• Could be made luminescent
• Supports surface electromagnetic waves
F. Bonaccorso et al., Nature Phot. 4, 611 (2010)
Graphene-based optoelectronics
LEDSolar cell
Flexible smart window
2.3%
Surface EM waves in graphene
Surface EM waves in graphene
Surface plasmons (SPs) in metallic surafces
Ligh
t con
e
SP
sW. L. Barnes et al., Nature 424, 824 (2003)
~ iqxe
~ x Le
q
qqq
SP
Surface EM waves in graphene
Conductivity of graphene
300T K0.2eV
Surface EM waves in graphene
Surface waves in graphene
~ iqxe
~ x Le
Im( ) 0
Im( ) 0
Surface EM waves in graphene
Graphene metamaterials and Transformation OpticsAshkan Vakil and Nader Engheta, arXiv: optics/1101.3585
Spatial varying voltage 2D graphene plasmonic prism
2D graphene plasmonic waveguide Transformation Optics devices
A point source: the fundamental problem
A point source: the fundamental problem
Possible sources for local excitation
molecule
quantum dot
Josephson qubit
A point source: the fundamental problem
Electric dipole
( )?E r
A point source: the fundamental problem
Computational difficulties: asymptotic approach
2( )
1
iqx
zp
eE x dq
q q
polebranch cutpole
branch cut
L. P. Felsen and N. Marcuvitz, Radiation and Scattering of Waves (IEEE Press, Piscataway, NJ, 1994)
Radiowave propagation problems
graphene
oscillating factor
Radiation patterns: SPs and free-space fields
Density of electromagnetic states
( ) ~ iqxE x dq DOS e
0.024 1.12
Radiation patterns: surface plasmons and free-space fields
Radiation patterns: SPs and free-space fields
Vertical dipole
0.31 , 0.97mm THz
SP characteristics:
SP 200L
Radiation patterns: SPs and free-space fields
Vertical dipole
41.3 , 7.2m THz
SP characteristics:
0.1SP 3L
Radiation patterns: SPs and free-space fields
Vertical dipole
1 ( 6.2 , 48.4 )m THz
2 ( 3.1 , 96.7 )m THz No SP excited
SP characteristics:
0.01SP 0.1L
No SP excited
Radiation patterns: SPs and free-space fields
Horizontal dipole
SP characteristics:• long propagation length• wavelength close to the vacuum one
0.31 , 0.97mm THz
Radiation patterns: SPs and free-space fields
Horizontal dipole
15.5 , 19.3m THz SP characteristics:• medium propagation length (of order of several wavelengths)• wavelength is quite less than the vacuum one
Radiation patterns: SPs and free-space fields
Horizontal dipole
No SP excited
3.1 , 96.7m THz
Possible applications
Possible applications
A. Gonzalez-Tudela et al., PRL 106, 020501 (2011)
Qubits coupling through graphene SPs waveguides
A. Vakil et al.,arXiv: optics/1101.3585
EM fields created by apertures in graphene
A. Yu. Nikitin et al., PRL 105, 073902 (2010)
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.
Conclusions