Nonlinear Plasmonics: Optics of Surface Plasmon Polariton Modes in an Optical Nanowire

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Nonlinear PlasmonicsOptics of Surface Plasmon
Polariton Modes in an Optical Nanowire
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Pout
Pin
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Outline

• Introduction.
• Linear optical properties of SPP modes.
• SPP resonances in isolated metallic structures.
• SPP modes in chains of nanoparticles.
• Application to nanodevices.
• Nonlinear effects.
• Dependence of mode transmission on optical power
  and material parameters.
• Optical limiting, frequency shifting, and
  switching.
• Applications to active nanodevices.
• Conclusions.

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Localized Surface Plasmon Polaritons

• Electron gas
• Metallic particles

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SPP Modes in Nanoparticle Chains

• E ? wires (or spheres) surface charge is
  induced.
• Oscillations of surface-charge density SPP
  resonances (localized).
• Coupling between SPP resonances on adjacent
  wires (tight-binding mechanism).
• Result propagating SPP modes (longitudinal, El,
  or transverse, Et).

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FDTD Calculations 2D and 3D

• Numerical approach
• Fields in grid described by full Maxwells eqs
  (FDTD) plus set of auxiliary diff. eqs. (ADE).
• Main grid surrounded by a perfectly absorbing
  layer.
• Mathematical description of material medium

This set of eqs, combined with Maxwells eqs, is
discretized on the Yees grid and marched in
time.
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Guiding in 2D Nanostructures
Field Profile of Plasmon Mode
Pulse prop. ( spectra) SPP excitation

• D 70 nm R 25 nm.
• ?p 13.7?1015 Hz ? 2.7?1013 Hz (Ag).
• ?t ? 320 nm (transverse mode).
• Geometry and material SPP spectra

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More Complex Nanodevices Y-splitter

• Extremely small size 0.6 ?m ? 0.8 ?m.
• Large losses intrinsic-metal and radiative
  losses
• Challenge to in-couple light.
• More complex devices possible.

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Chains of Metallo-Dielectric Nanoshells

• D 70 nm R 25 nm t 10 nm.
• ns 1.5 nb 1.
• ?p 13.7?1015 Hz ? 2.7?1013 Hz (Ag).
• ?r 6.6 ?1015 Hz (localized SPP resonance).
• ?abs ltlt ?ext.

• Up to 300x field enhancement.
• Expect strong nonlinear effects.

• Quasistatic approximation
• Isolated nanoshell

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Comparing SPP Propagating Modes Linear Limit

• Two SPP modes longitudinal and transverse.
• ?l 5.98?1015 Hz ?t 5.63?1015 Hz.
• ?l 10.2?106 m1 ?t 7.7?106 m1.
• Nanoparticles with elongated shape, reduce
  losses by ?10.

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Nonlinear Effects

• Mode frequency shift
• n2 1.5?1017 m2/W (polymer range).
• SPP mode frequency depends on propagating power
  P.
• Change in frequency decreases with propagation
  distance.
• ?? ?150 THz for P ?0.6 mW.
• Optical Limiting
• Transmission strongly increases (or decreases)
  with mode power due to shift in mode frequency.

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Nonlinear Effects

• Self-phase modulation
• Pulse develops additional series of maxima.
• Also, mode frequency shifts.
• Fix P 100 MW/cm2, vary n2.

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Conclusions

• SPP modes can be employed in ultrashort
  nanodevices, i.e. dimensions of wavelengths.
• Excitation of SPP modes provides field
  enhancement for nonlinear-optical processes.
• Nonlinear effects such as frequency shifting,
  optical limiting, and self-phase modulation occur
  in optical metallo-dielectric nanowire.
• Provides route to active plasmonic devices.