Udagedara Indika B, Rukhlenko Ivan D, Premaratne Malin
Advanced Computing and Simulation Laboratory, Department of Electrical and Computer Systems Engineering,Monash University, Clayton, VIC 3800, Australia.
Opt Express. 2011 Oct 10;19(21):19973-86. doi: 10.1364/OE.19.019973.
The energy transport properties of plasmonic waveguides can be analyzed by solving the dispersion relation for surface plasmon-polaritons (SPPs). We use this approach to derive an approximate analytical expression for SPP propagation length when the waveguide is composed of linearly arranged metallic nanoparticles, while assuming that metal losses are small or partially compensated by gain. Applied to metal-dielectric (composite) nanospheres, the obtained expression allows us to optimize the performance of the waveguide and arrive at a number of practical design rules. Specifically, we show that SPP attenuation can be minimized at a certain interparticle distance for transverse modes, but gradually grows for both longitudinal and transverse modes with the increase of particle separation. We also show that the two basic methods of supplying gain to the system, i.e., embedding the particles into a gain medium or having a metal-gain composition for the particles, do not perform equally well and the former method is more efficient, but the way the two methods affect depends on the polarization of SPPs. To investigate the role of the nanoparticles' arrangement in determining SPP characteristics, we follow a purely numerical approach and consider a two-segment bent waveguide as an example. Analyzing the waveguide's transmission shows that it behaves in an oscillatory manner with respect to the angle between the two segments and is therefore higher for certain angles than for the others. This suggests that, in the design of waveguides with bends, careful attention needs to be paid in order to avoid bend angles that yield low transmission and to choose angles that give maximum transmission.
表面等离激元极化激元（SPP）的色散关系求解可用于分析等离激元波导的能量传输特性。我们采用这种方法，在假设金属损耗较小或被增益部分补偿的情况下，推导了由线性排列的金属纳米颗粒组成的波导中SPP传播长度的近似解析表达式。将所得表达式应用于金属 - 介质（复合）纳米球，可优化波导性能并得出一些实用的设计规则。具体而言，我们表明对于横向模式，在特定的粒子间距下SPP衰减可降至最低，但随着粒子间距增加，纵向和横向模式的衰减都会逐渐增大。我们还表明，向系统提供增益的两种基本方法，即将粒子嵌入增益介质或使粒子具有金属 - 增益成分，效果并不相同，前一种方法更有效，但两种方法的影响方式取决于SPP的极化。为了研究纳米颗粒排列在确定SPP特性中的作用，我们采用纯数值方法，以两段弯曲波导为例进行分析。对波导传输的分析表明，其传输行为随两段之间的夹角呈振荡变化，因此在某些角度下传输高于其他角度。这表明，在设计弯曲波导时，需要特别注意避免出现导致低传输的弯曲角度，并选择能实现最大传输的角度。
