Nanoplasmonic Array Enhancement of Two-Photon Absorption in a Dye Film

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• 作者：Jarrett H. Vella ; Augustine M. Urbas
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：August 16, 2012
• 年：2012
• 卷：116
• 期：32
• 页码：17169-17173
• 全文大小：235K
• 年卷期：v.116,no.32(August 16, 2012)
• ISSN：1932-7455

文摘

We investigate the enhancement of the effective two-photon absorption cross section of a film of an organic dye by a plasmonic triangular prism array through finite element calculations and experimental measurements. Hexagonal arrays of plasmonic triangular prism arrays were prepared using nanosphere lithography so that their localized surface plasmon resonance (LSPR) is at 800 nm. A dye, AF455, with significant two-photon fluorescence when excited at 800 nm was spin-coated onto the plasmonic array. Several film thicknesses of AF455 were prepared, ranging from 40 to 184 nm. The dependence of the effective two-photon absorption cross section 蟽⁽²⁾ of AF455 on the thickness of the dye layer was measured using a newly applied technique. Because two-photon fluorescence is only sensitive to light absorbed by the chromophore, absorption from the nanostructure, thermal effects, and other parasitic optical mechanisms that could indicate anomalously high 蟽⁽²⁾ enhancement values are eliminated from the measured enhancement. The results quantitatively agreed with the 蟽⁽²⁾ enhancement values predicted by finite element method (FEM) calculations. The simulations show that the 蟽⁽²⁾ enhancement observed was due to the plasmonic triangular prism arrays鈥?LSPR and that the dependence of 蟽⁽²⁾ of AF455 on the gold nanostructure is influenced by an optical reflection pattern generated by the plasmonic array in addition to the near-field enhancement. The combination of theory and experiments validates the application of the technique to 蟽⁽²⁾ enhancement measurements.