Lecture 11 - Guiding Light Along Nanoparticle Arrays

Lecture 11 - Guiding Light Along Nanoparticle Arrays -...

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Lecture 11: Guiding Light Along Nanoparticle Arrays 5 nm
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E H What happened at the last Lecture Coupling light to surface plasmon-polaritons Kretchman geometry Grating coupling //, Air sp m = ± kk G 2 //, sin SiO d sp c ω εθ = = Θ Coupling from a metal dot Guiding geometries Stripes and wires Line defects in hexagonal arrays (2d photonic crystals) Today: nanoparticle arrays
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S.A. Maier, M.L. Brongersma H.A. Atwater, Appl. Phys. Lett. 78, 16, 2001 Light and microwaves are electromagnetic waves described by Maxwell’s equations SEM of array of 50 nm Au particles λ = 600 nm, ω = 3.1x10 15 rad/s d = 75 nm Near field optical excitation 600 nm Guiding of light along an array of Au nanoparticles ?
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A cm-scale Analogue to a Plasmonic Device 8 GHz z = 3.7 cm d = 2 mm h = 1.4 cm 101 Cu rods Experimental setup 90% of the energy is confined within a distance of 0.05 λ F 3-4 dB loss at a corner due far-field radiation - 1012345 -2 -1 0 1 2 3 x (wavelengths) y (wavelengths) source -1 0 0 I/I 0 (dB) x (wavelengths) 0 1 λ 2 λ 3 λ -1 λ -2 λ -1 λ 0 1 λ 3 λ 4 λ 5 λ 2 λ X Y Plot of |E z | on a logarithmic scale 0- 1 2 0 -10 -20 0 0 -10 Stefan A. Maier et al., Appl. Phys. Lett. 78, 16, 2001
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Light can penetrate metallic nanoparticles and set the electrons in motion This collective electron motion is called a plasmon 50 nanometer Au, Ag, or Cu particle E field + - - - + + + + - - + ++ + - - - - - + + ++ + - - - - - + + + + + + - - - - - + + + + + - - - - - + + + + + - - - - - + + + + + - - - - - + + + + + - - - - - + + + + + - - - - - + ++ + - - - - - + + + + + + - - - - - Mode size << λ Loss per unit length 3 dB/ μ m …. Loss per device may be manageable Plasmonics: Guiding “light” along metallic nanostructures EM Near-field Interaction between Nanoparticles
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Excitation of a Single Metal Nanoparticle () ( ) () () 1, 3/2 0 2 2 2, 9 2 M abs H MH M V c εω ω σω ε ωε = ⎡⎤ ++ ⎣⎦ 2 H n ε M = ε 1,M + i ε 2,M ε H = ε 1,H = Volume = V 0 Particle Host matrix E-field + + + - - - - - 300 400 500 600 700 800 900 0 100 200 n=3.3 n=1.5 1 R = 5 nm σ ext (nm 2 ) λ (nm) 4 3.5 3 2.5 2 1.5 Energy (eV) Ag cluster D = 10 nm G. Mie Ann. Phys. 25, 377 (1908) abs
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Origin Enhanced Absorption Cross-section Energy flux (Poynting vector) for a plane wave incident on a metallic nanoparticle Poynting vector Off resonance On resonance σ abs C. F. Bohren, D. R. Huffman, Absorption and Scattering of Light by Small Particles, Wiley, New York 1983
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Properties of a Chain of Metal Nanoparticles Near-field interaction sets up dipole (plasmon) waves Two types: Transverse (T) & Longitudinal (L) modes E P = E F + E M + E R Where E F R -3 Förster field E M R -2 E R R -1 Radiation field When d << λ Förster field dominant Ö n.n. interaction dominates Interaction strength related to dipole field E P •• m-3 m-2 m-1 m m+1 m+2 m+3 m+4 m+5 ••••• p m d
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This note was uploaded on 01/10/2011 for the course ECE 695s taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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Lecture 11 - Guiding Light Along Nanoparticle Arrays -...

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