Nanoantennas with balanced gain and loss
Nanoantennas with balanced gain and loss
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DOI：
10.1515/nanoph-2019-0392
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发表时间：
2019-12
期刊：
影响因子：
7.5
通讯作者：
S. Sanders;A. Manjavacas
中科院分区：
文献类型：
--
作者：
S. Sanders;A. Manjavacas
金属纳米结构的等离子体共振所提供的大截面和强约束使这些系统成为实现纳米天线的理想平台。就像它们的宏观对应物一样，纳米天线增强了深亚波长发射器和自由辐射之间的耦合，同时提供了增加的方向性。在这里，受奇偶时间对称等离子体的启发，我们研究了如何将传统的等离子体纳米结构与活性材料相结合，在外部泵浦时显示光学增益，从而提高金属纳米天线的性能。我们发现，增益的存在，除了减轻损耗并因此增加发射器辐射或吸收的功率外，还引入了纳米天线元件之间的相位差，即使在没有几何不对称的情况下，也会使系统的光学响应具有方向性。利用这些特性，我们分析了一对增益和损耗平衡的纳米天线如何增强两个偶极子发射器之间的远场相互作用。这项工作的结果对由主动和被动等离子体纳米结构制成的纳米天线的光学响应提供了有价值的见解，具有设计能够在纳米尺度上主动控制光的光学器件的潜在应用。
Abstract The large cross sections and strong confinement provided by the plasmon resonances of metallic nanostructures make these systems an ideal platform to implement nanoantennas. Like their macroscopic counterparts, nanoantennas enhance the coupling between deep subwavelength emitters and free radiation, providing, at the same time, an increased directionality. Here, inspired by the recent works in parity-time symmetric plasmonics, we investigate how the combination of conventional plasmonic nanostructures with active materials, which display optical gain when externally pumped, can serve to enhance the performance of metallic nanoantennas. We find that the presence of gain, in addition to mitigating the losses and therefore increasing the power radiated or absorbed by an emitter, introduces a phase difference between the elements of the nanoantenna that makes the optical response of the system directional, even in the absence of geometrical asymmetry. Exploiting these properties, we analyse how a pair of nanoantennas with balanced gain and loss can enhance the far-field interaction between two dipole emitters. The results of this work provide valuable insight into the optical response of nanoantennas made of active and passive plasmonic nanostructures, with potential applications for the design of optical devices capable of actively controlling light at the nanoscale.