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Anomalous surface plasmon dispersion in aluminum

Anomalous surface plasmon dispersion in aluminum

Talk I gave at Casimir Spring School 2012

Philip Chimento

June 15, 2012
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  1. Anomalous
    surface plasmon
    dispersion
    in
    aluminum
    Eric Eliel Gert ‘t Hooft Philip Chimento
    >ĞŝĚĞŶhŶŝǀĞƌƐŝƚLJͻYƵĂŶƚƵŵKƉƟĐƐ
    @therealptomato
    { }

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  2. { Surface plasmons }

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  3. Quick explanation of them
    Surface plasmons
    Using English literature

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  4. in English literature
    Image: public domain
    Surface plasmons
    Dr. Edwin Abbott Abbott,
    author of...

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  5. “Flatland”

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  6. “Flatland”
    A surface plasmon polariton is what a
    light wave would be in Flatland

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  7. “Flatland”
    A surface plasmon polariton is what a
    light wave would be in Flatland

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  8. Exist on the interface between a metal and a dielectric
    Surface plasmons

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  9. Can be excited using light, but not directly
    Surface plasmons

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  10. Can be excited using light, but not directly
    Surface plasmons

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  11. A surface plasmon on a metal-air interface has more
    momentum than a photon with the same energy in air
    Surface plasmons

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  12. A photon in a denser medium can match the momentum of a
    surface plasmon on a metal-air interface
    Surface plasmons

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  13. Attenuated total reflection — “Kretschmann configuration”
    ATR Coupling

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  14. Evanescent waves from the total internal reflection cross the
    metal and couple to plasmons on the other side
    ATR Coupling

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  15. { That was easy }

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  16. It’s a question of “the least bad”
    Metals for plasmonics

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  17. Aluminum is one of the “least bad”
    Metals for plasmonics

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  18. Rakic et al., Appl. Opt. 37, p. 5271 (1998)
    Aluminum has an interband transition that absorbs at 800 nm
    Aluminum

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  19. E ective mode index of plasmons on an aluminum surface
    Aluminum plasmons
    īĞĐƟǀĞ^WŝŶĚĞdž

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  20. have a region of anomalous dispersion
    Aluminum plasmons
    īĞĐƟǀĞ^WŝŶĚĞdž
    Anomalous  
    dispersion

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  21. Experiment
    Exciting plasmons on aluminum by ATR coupling
    ϱŶŵ^ŝ
    3
    N
    4
     
    ƉƌŽƚĞĐƟŽŶůĂLJĞƌ
    ϳ͕ϵ͕ϭϮ͕ϭϯŶŵů
    <ϳŐůĂƐƐ

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  22. Measure reflection as a function of angle
    Experiment
                                                 ^ŽƵrĐe                                                                                                        
                                                                                                         DeteĐtŽr
                       ɽ                                  ɽ

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  23. We measure hundreds of one-wavelength curves like these...
    Experiment

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  24. ...to get a dispersion curve like this
    Experiment
    īĞĐƟǀĞ^WŝŶĚĞdž

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  25. The results were less than inspiring for a 9 nm layer
    Plasmon dispersion

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  26. For a 12 nm layer, the dispersion was anomalous but less
    than expected
    Plasmon dispersion
    īĞĐƟǀĞ^WŝŶĚĞdž

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  27. Novotny et al., J. Nanophotonics 5 (2011)
    Thin-layer aluminum doesn’t have the same optical properties
    as bulk aluminum
    What’s going on?
    ďƵůŬ

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  28. Thicker aluminum layer behaves more like bulk aluminum, but
    diminishes the ATR e ect
    How to fix it?

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  29. Thicker aluminum layer behaves more like bulk aluminum, but
    diminishes the ATR e ect
    How to fix it?
    The evanescent
    waves evanesce
    before they reach
    the top

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  30. You have to be crazy to do it, but: the Otto configuration
    How to fix it?

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  31. Crazy?
    Relative size of
    a dust particle,
    20 µm
    Gap size, 1 µm

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  32. Luckily, that problem is solvable
    How to fix it?
    ŚŝŐŚͲŝŶĚĞdžĚŝĞůĞĐƚƌŝĐ
    ůŽǁͲŝŶĚĞdž
    ĚŝĞůĞĐƚƌŝĐ

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  33. { Thanks }
    Fruitful discussions
    Michiel de Dood
    Wolfgang Lö er
    Kind assistance
    Daan Boltje
    Klara Uhlirova

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