Surface plasmon polaritons SPP and their use in subwavelength optics

1
Surface plasmon polaritons (SPP) and their use in
subwavelength optics

• Luis Prill Sempere

2
Outline

• Introduction
• What are SPPs?
• Ways of excitation
• Enhanced transmission through nano apertures
• SPP bandgap
• Nano optic devices
• Nano lenses
• Summary

3
Introduction
Optical devices become smaller and
smaller Structures smaller than ?/2 do not act
as desired New optics have to be found for
subwavelength regime SPP-manipulation instead of
photon manipulation SPP work together with
electric devices because metallic
4
What are SPPs?
Surface Plasmon Polaritons are charge density
waves on the surface of materials with free
electrons (metals, plasmas, etc.) propagating
along the interface of this conductor and a
dielectric medium
Oscillating electric fields can excite SPPs SPP
field decays exponentially with distance to
surface
5
What are SPPs?
6
Ways of excitation
from Maxwell equation
momentum mismatch between photon and SPPs
7
Ways of excitation

• total internal reflection
• periodic corrugations
• scattering on topological defects

8
Ways of excitation

• total internal reflection
• periodic corrugations
• scattering on topological defects

9
Enhanced transmission through nano apertures
(1998)
Ebbesen et al Extraordinary optical transmission
through sub-wavelength hole arrays. Nature 391,
667669 (1998).

• Nano apertures in plane metal surface
• Periodic holes convert photons in SPPs
• SPPs reemit photons behind metal

10
Enhanced transmission through nano apertures

• ?326nm? normal bulk silver plasmon
• ?1370nm highest peak
• transmission efficiency 2
• hole -periodicity?changes postion of peaks
• t/d ratio ? changes peak width

11
SPP bandgap
At a ?SPP/2 we get 2 standing waves with
different ? Energies in between ? and ?- are
not allowed
12
Nano optic devices (2002)
Ditlbacher et al. Two-dimensional optics with
surface plasmon polaritons. Appl. Phys. Lett. 81,
17621764 (2002).

• Experimental setup (top-bottom)
• double-arrow ? light polarization
• arrangement of the nano-optic devices
• Atomic Force Microscope

• SPPs
• travel several 100nm
• reconvert into photons
• Manipulation of SPPs instead of photons leads to
  nano-optics
• mirrors and beam-splitter are demonstrated

13
Nano optic devices
Laser on nano-wire excites 2 SPPs
Laser ? 750nm P 5mW Nano-wire width
160nm length 20 ?m SPPs propagates in
direction of light polarization ? SPP 610nm
Nanoparticles build a bragg reflector
Nanoparticles diameter 140nm 5 lines with
350nm distance at 60? Seprataion of particles
220nm
(a) SEM (b) fluorescence image (PMMA)
14
Nano optic devices
Single line of nanoparticles creates a beam
splitter
Line of nanoparticles Diameter
140nm Separation 280nm
Add second mirror to create interferometer
(a) interference with 2 mirror (b) Right mirror
moved by 300nm Reflective and transmitted beam
seem phaseshifted
15
Nano lenses (2004)
Sun et al. Refractive transmission of light and
beam shaping with metallic nano-optic lenses.
Appl. Phys. Lett 85, 642-644

• photons creates SPPs
• SPP travels through hole
• SPP reemits photon
• Equally distributed lightfield

Slit width 80nm Layer thickness 200nm Laser ?
650nm
16
Nano lenses
from Maxwell equations
(a) refractive index over wavelength (b)
transmittance A over slit depth. (c) phase over
slit depth. (b) and (c) the slit width is
around 80nm and ? 650nm.
17
Nano lenses
Phase shifting creates lens effects Collimation
and focusing demonstrated Focal length slit
number No edge effect

• 2µm wide convex bump
• Slit width 80nm
• Slit depths
• 700nm and 750nm
• (b) Slit depths
• 450nm, 700nm and 750nm

18
Summary

• SPPs seem to be a good way to circumvent the
  problems with subwavelength optics
• Mirrors, beamsplitter and lenses in nanoscale are
  possible
• Future will bring more optical devices
• Combination with existing optical bio sensors
  imaginable
• Optical data storage can be enhanced
• Combination with electric devices possible

19
References
1. Ritchie, R. H. Plasma losses by fast electrons
in thin films. Phys. Rev. 106, 874881 (1957). 2.
Ebbesen, T. W., Lezec, H. J., Ghaemi, H. F.,
Thio, T. Wolff, P. A. Extraordinary optical
transmission through sub-wavelength hole arrays.
Nature 391, 667669 (1998). 3. Ditlbacher, H.,
Krenn, J. R., Schider, G., Leitner, A.
Aussenegg, F. R. Two-dimensional optics
with surface plasmon polaritons. Appl. Phys.
Lett. 81, 17621764 (2002). 4. Zhijun Sun and
Hong Koo Kim, Refractive transmission of light
and beam shaping with metallic nano-optic lenses.
Appl. Phys. Lett 85, 642-644 (2004) 5. W. L.
Barnes, A. Dereux, and T. W. Ebbesen. Surface
plasmon subwavelength optics. Nature 424, 824
(2003). 6. Sambles, J. R., Bradbery, G. W.
Yang, F. Z. Optical-excitation of
surface-plasmons - an introduction. Contemp.
Phys. 32, 173183 (1991). 7. Martín-Moreno, L. et
al. Theory of extraordinary optical transmission
through subwavelength hole arrays. Phys. Rev.
Lett. 86, 11141117 (2001). 8. Bethe, H. A.
Theory of diffraction by small holes. Phys. Rev.
66, 163182 (1944). 9. Propagating modes in a
metal-clad-dielectric-slab waveguide structure
had previously been analyzed for the case that
the penetration depth into metal clads is
negligible compared to the dielectric slab
thickness. See, for example, T. Takano and J.
Hamasaki, IEEE J. Quantum Electron. QE-8, 206
(1972). In the present work, we analyzed the
nanoslit structure by taking into account the
effect of field penetration into the metal region
without any approximation. 10. T. Thio, K. M.
Pellerin, R. A. Linke, H. J. Lezec, and T.
W.Ebbesen. Enhanced light transmission through a
single subwavelength aperture. Opt. Lett. 26,
1972 (2001). 11. Schultz A. Plasmon resonant
particles for biological detection. Current
Opinion in Biotechnology 14, 13-22 (2003) 12.
Amanda J. Haes, W. Paige, Richard P. Van Duyne. A
Localized Surface Plasmon Resonance Biosensor
First Steps toward an Assay for Alzheimers
Disease. Nano Letters 4, 1029-1034 (2004) 13.
Schaadt DM, Feng B, Yub ET. Enhanced
semiconductor optical absorption via surface
plasmon excitation in metal nanoparticles, Appl.
Phys. Lett 86, Art. No. 063106 (2005)