Department of Chemistry, Laboratory for Nanophotonics, Rice University, Houston, Texas 77005, United States.
ACS Nano. 2012 Sep 25;6(9):8105-13. doi: 10.1021/nn3027112. Epub 2012 Aug 28.
A comprehensive understanding of the type of modes and their propagation length for surface plasmon polaritons (SPPs) in gold nanowires is essential for potential applications of these materials as nanoscale optical waveguides. We have studied chemically synthesized single gold nanowires by a novel technique called bleach-imaged plasmon propagation (BlIPP), which relies on the plasmonic near-field induced photobleaching of a dye to report the SPP propagation in nanowires. We observed a much longer propagation length of 7.5 ± 2.0 μm at 785 nm compared to earlier reports, which found propagation lengths of ~2.5 μm. Finite difference time domain simulations revealed that the bleach-imaged SPP is a higher order m = 1 mode and that the lowest order m = 0 mode is strongly quenched due to the loss to the dye layer and cannot be resolved by BlIPP. A comparative assessment of BlIPP with direct fluorescence imaging furthermore showed that the significant difference in propagation lengths obtained by these two techniques can be attributed to the difference in their experimental conditions, especially to the difference in thickness of the dye layer coating on the nanowire. In addition to identifying a higher order SPP mode with long propagation length, our study infers that caution must be taken in selecting indirect measurement techniques for probing SPP propagation in nanoscale metallic waveguides.
全面了解金纳米线中表面等离激元（SPP）的模式类型及其传播长度，对于这些材料作为纳米尺度光学波导的潜在应用至关重要。我们通过一种称为漂白成像等离子体传播（BlIPP）的新技术研究了化学合成的单根金纳米线，该技术依赖于等离子体近场诱导染料的光漂白，以报告纳米线中 SPP 的传播。我们观察到在 785nm 处的传播长度比之前报道的 785nm 时的传播长度长很多，为 7.5±2.0μm，而之前报道的传播长度约为 2.5μm。有限差分时域模拟表明，漂白成像 SPP 是一种高阶 m=1 模式，由于染料层的损耗，最低阶 m=0 模式被强烈猝灭，无法通过 BlIPP 分辨。BlIPP 与直接荧光成像的比较评估进一步表明，这两种技术获得的传播长度的显著差异可归因于它们的实验条件的差异，尤其是纳米线上染料层涂层厚度的差异。除了确定具有长传播长度的高阶 SPP 模式外，我们的研究还推断，在选择用于探测纳米尺度金属波导中 SPP 传播的间接测量技术时必须谨慎。
