Plasmonics

Review & Survey of the Latest Research

By Alexander Pourshalchi

Two Excitations

• Localized Surface Plasmon Resonance

• Optical Excitation must be tuned to the plasma resonance of the metal which is dependant on the environment

• Negative Real part of the refractive dielectric permittivity ε, positive imaginary (absorption)

• Surface Plasmon Polaritons– Propagating surface Plasmon

oscillations

• Pros:– Several order of magnitude

field enhancement– Field Confinement– Dependant of environment

(tunability)– Efficient coupling– Highly dispersive?– Low Noise

• Cons:– Lossy– Thermal Effects

Localized Surface PlasmonsField Distribution in the Vicinity of the spherical metal

nanoparticle (Z polarized incident field)

Extinction spectra of an Optical Field E incident on the spherical nanoparticle

Visual Representation

Drude Model:

Applications

• Spectroscopy• Molecular detection (SERS)• Effective Killing of Cancer cells

Limitations:

•Nanofabrication techniques of varying size shape material is limiting the technology

• Difficult to design antigens to attract antibodies.

•In-vitro controlling of nanoparticles.

Surface Plasmon Polaritons

Three efficient coupling configurations

• Kretchman / Reverse Kretchman

• Otto

Grating Coupled

Dispersion Relation

Why?To invent new photonic devices that take advantage of the

unique properties of SPPs.• Recall:

– Several order of magnitude field enhancement• Enhanced Nonlinearities

– Field Confinement• Nanophotonics (Reduced device footprint)

– Dependant of environment • Tunability

– Efficient coupling– Highly dispersive

• Limitations:– Lossy– Thermal Effects– Nanofabrication techniques limit structure dimensions– Difficult to simulate.

Latest Applications

• Integrated Beam collimation of Sub-wavelength aperture lasers (QCL’s)– Capasso et al. @ SEAS Harvard 2007.

Grooves contribute to far field intensity through interference

effectsλ laser is 9.9μm

More Applications

• Near field optical microscopy• Optical Data Storage- Super resolution near field

structure• Nanophotonics• 4 Wave mixing• Solar Cells?• Surface plasmon coupled emission• Surface plasmon enhanced photodetectors.• Photonic Metamaterials (filters/super absorption)

NanoPhotonic Applications of SPPs

1. How to couple/ Generate into SPP modes.• Already discussed. Any novel methods?

2. What modes exists?• Symmetric/ Asymmetric bound modes

3. How the modes propagate• Bending losses/ Bragg Reflectors.

4. Perform some useful function• All optical signal processing• Wavelength Division Multiplexing• Spectroscopy and or Ultra short Pulse Characterization

5. Couple back into optical modes.• Symmetric modes waveguide taper results in a Gaussian

output.

Nanophotonics

• Plasmonics offers a bridge from ultrafast but diffraction limited optics to nanometer confined but low bandwidth electronics.

Optical Vortices

• Phase Modulations of incident light results in spatial manipulation of SPPs. (Beam Steering)

Femtosecond pulses coupled into SPPs?

• Group Velocity Dispersion results in temporal pulse broadening

• Loss Dispersion results in temporal pulse narrowing

• The effects occur simultaneously.

• Material choice is critical.

Optical Wideband A/D converter

Plasmonic SLM

• Subwavelength Hole Arrays

• How do we address each pixel at a refresh rate at 10MHz?

• Electro Optics?– Already been investigated, only As2S3

Showed promise, yet nanofabrication techniques limited samples.