Anomalous surface plasmon dispersion in aluminum

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Anomalous surface plasmon dispersion in aluminum Eric Eliel Gert ‘t Hooft Philip Chimento >ĞŝĚĞŶhŶŝǀĞƌƐŝƚǇͻYƵĂŶƚƵŵKƉƟĐƐ @therealptomato { }

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{ Surface plasmons }

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Quick explanation of them Surface plasmons Using English literature

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

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“Flatland”

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

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

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

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Can be excited using light, but not directly Surface plasmons

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Can be excited using light, but not directly Surface plasmons

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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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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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Attenuated total reﬂection — “Kretschmann conﬁguration” ATR Coupling

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

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{ That was easy }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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