Department of Physics and CNR - Nanotec, University of Calabria , 87036 Rende, Italy.
Colegio de Ciencias e Ingenieria, Universidad San Francisco de Quito , 170150 Quito, Ecuador.
ACS Nano. 2017 Jan 24;11(1):1012-1025. doi: 10.1021/acsnano.6b07638. Epub 2016 Dec 30.
We present a detailed study on the resonant gain (RG) phenomena occurring in two nanostructures, in which the presence of dielectric singularities is used to reach a huge amplification of the emitted photons resonantly interacting with the system. The presence of gain molecules in the considered nanoresonator systems makes it possible to obtain optical features that are able to unlock several applications. Two noticeable cases have been investigated: a 1D nanoresonator based on hyperbolic metamaterials and a 3D metal/dielectric spherical multishell. The former has been designed in the framework of the effective medium theory, in order to behave as an epsilon-near-zero-and-pole metamaterial, showing extraordinary light confinement and collimation. Such a peculiarity represents the key to lead to a RG behavior, a condition in which the system is demonstrated to behave as a self-amplifying perfect lens. Very high enhancement and spectral sharpness of 1 nm of the emitted light are demonstrated by means of a transfer matrix method simulation. The latter system consists of a metal/doped-dielectric multishell. A dedicated theoretical approach has been set up to finely engineer its doubly tunable resonant nature. The RG condition has been demonstrated also in this case. Finite element method-based simulations, together with an analytical model, clarify the electric field distribution inside the multishell and suggest the opportunity to use this device as a self-enhanced loss compensated multishell, being a favorable scenario for low-threshold SPASER action. Counterintuitively, exceeding the resonant gain amount of molecules in both systems causes a significant drop in the amplitude of the resonance.
我们对两种纳米结构中发生的共振增益（RG）现象进行了详细研究，其中介电奇点的存在被用来实现与系统共振相互作用的发射光子的巨大放大。在所考虑的纳米谐振器系统中存在增益分子，使得能够获得能够解锁多种应用的光学特性。已经研究了两个显著的情况：基于双曲超材料的 1D 纳米谐振器和 3D 金属/介电球形多壳层。前者是在有效媒质理论的框架内设计的，以便表现为 ε 近零和极点超材料，表现出非凡的光限制和准直。这种特殊性是导致 RG 行为的关键，在这种情况下，系统被证明表现为自放大完美透镜。通过传输矩阵方法模拟证明了发射光的非常高的增强和 1nm 的光谱锐度。后者系统由金属/掺杂介电多壳层组成。已经建立了一种专用的理论方法来精细地设计其双重可调谐共振性质。在这种情况下也证明了 RG 条件。基于有限元方法的模拟以及分析模型，阐明了多壳层内的电场分布，并提出了将该器件用作自增强损耗补偿多壳层的机会，这是低阈值 SPASER 作用的有利情况。反直觉的是，在这两种系统中超过分子的共振增益量会导致共振幅度的显著下降。
