Alù Andrea, Engheta Nader
Department of Electrical and Computer Engineering, University of Texas at Austin, 1 University Station C0803, Austin, TX 78712, USA.
Department of Electrical and Systems Engineering, University of Pennsylvania, 200 South 33rd St., Philadelphia, PA 19104, USA.
Materials (Basel). 2011 Jan 4;4(1):141-152. doi: 10.3390/ma4010141.
Enhancement of molecular emission is usually obtained by coupling small optical emitters with external resonant structures and systems, as first established by Purcell several decades ago, and verified in several recent investigations using molecules or quantum dots coupled with plasmonic nanoantennas. Here we theoretically investigate in detail a different mechanism for emission enhancement, based on our recent idea of a plasmonic nanolauncher [Phys. Rev. Lett. 2009, 103, 043902], i.e., a metamaterial-inspired ultranarrow waveguide channel operating near its cut-off frequency. Such system is not necessarily at resonance, but its peculiar operation may provide enhanced emission over a relatively broad physical area, which may allow enhancement of emission independent of the position of an individual or of a group of molecules along such plasmonic channel, and the possibility to bend and route the emitted energy with large flexibility. We present here extensive theoretical and numerical results that confirm this intuition and may envision a novel method for molecular emission enhancement at the nanoscale, with more flexibility than the conventional Purcell resonance techniques.
分子发射的增强通常是通过将小型光发射器与外部共振结构及系统耦合来实现的，这是几十年前由珀塞尔首次提出的，并在最近几项使用与等离子体纳米天线耦合的分子或量子点的研究中得到了验证。在此，我们基于我们最近提出的等离子体纳米发射器的概念[《物理评论快报》2009年，第103卷，043902]，从理论上详细研究了一种不同的发射增强机制，即一种受超材料启发的超窄波导通道，其在截止频率附近工作。这样的系统不一定处于共振状态，但其独特的运行方式可能在相对较大的物理区域内提供增强的发射，这可能使得发射增强与单个或一组分子沿着这种等离子体通道的位置无关，并且有可能以很大的灵活性弯曲和引导发射能量。我们在此展示了广泛的理论和数值结果，这些结果证实了这一直觉，并可能预想一种在纳米尺度上增强分子发射的新方法，该方法比传统的珀塞尔共振技术具有更大的灵活性。
