Gain in negative-index metamaterials and slow-light waveguides
Gain in negative-index metamaterials and slow-light waveguides
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DOI：
10.1117/12.871948
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发表时间：
2010-08
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通讯作者：
S. Wuestner;E. Kirby;Andreas Pusch;K. Tsakmakidis;J. Hamm;O. Hess
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作者：
S. Wuestner;E. Kirby;Andreas Pusch;K. Tsakmakidis;J. Hamm;O. Hess
基于全三维时空麦克斯韦-布洛赫方法，研究了非双各向异性负折射率（NRI）超材料中完全损耗补偿的可能性。我们表明，明智地将光泵浦增益材料，如激光染料，结合到双渔网超材料中，可以在所得有效折射率（″中n = n ‘ +）的实部n ’为负的情况下获得增益。结果表明，存在一个实际的光学几何和材料（增益/损耗）参数的频带，其中n ' < 0和同时n″< 0保持不变，从而导致在两个不同的频率点上发散的品质图。在确保微观、元分子水平上，在考虑的光频率范围内，可以获得实际水平的损耗和增益，我们探索了补偿负折射率慢光超材料异质结构中传播损耗的可能性。该异质结构由一个负折射率的核心层组成，核心层被两个薄的有源包层对称地包住，为传播的慢光脉冲提供倏逝增益。结果表明，反向传播的光-具有反平行的相速度和群速度，并且经历负的有效折射率-可以在这种慢光波导结构中被放大。我们的研究结果提供了一个直接和明确的证据，证明在非双向异性折射率为负的情况下，在微观和宏观水平上，完全补偿损失和获得增益是可能的，特别是在导光传播缓慢的情况下。
We investigate on the basis of a full three-dimensional spatio-temporal Maxwell-Bloch approach the possibility of complete loss compensation in non-bianisotropic negative refractive index (NRI) metamaterials. We show that a judicious incorporation of optically pumped gain materials, such as laser dyes, into a double-fishnet metamaterial can enable gain in the regime where the real part n′ of the resulting effective refractive index (n = n′ + in″) is negative. It is demonstrated that a frequency band exists for realistic opto-geometric and material (gain/loss) parameters where n′ < 0 and simultaneously n″ < 0 hold, resulting in a figure-of-merit that diverges at two distinct frequency points. Having ensured on the microscopic, meta-molecular level that realistic levels of losses and even gain are accessible in the considered optical frequency regime we explore the possibility of compensating propagation losses in a negative refractive index slow-light metamaterial heterostructure. The heterostructure is composed of a negative refractive index core-layer bounded symmetrically by two thin active cladding layers providing evanescent gain to the propagating slow light pulses. It is shown that backward-propagating light - having anti-parallel phase and group velocities and experiencing a negative effective refractive index - can be amplified inside this slow-light waveguide structure. Our results provide a direct and unambiguous proof that full compensation of losses and attainment of gain are possible on the microscopic as well as the macroscopic level in the regime where the non-bianisotropic refractive index is negative - including, in particular, the regime where the guided light propagates slowly.