Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range
Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range
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DOI：
10.1088/0022-3727/49/8/085105
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发表时间：
2016-01
期刊：
影响因子：
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通讯作者：
A. Danicic;J. Radovanović;S. Ramović;V. Milanovic
中科院分区：
文献类型：
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作者：
A. Danicic;J. Radovanović;S. Ramović;V. Milanovic
为了避免由金属夹杂物引起的超材料单元电池在感兴趣频率上的损耗，提出了一种有源介质设计。作为这种活性介质的候选结构，我们选择了量子级联激光器，因为它们具有高输出增益。在这里，我们分析和比较了两种量子级联结构，它们分别在强磁场的影响下发射4.6太赫兹和3.9太赫兹。我们首先求解了所有相关朗道能级的完整速率方程组，并获得了能级间载流子分布的必要信息，然后我们就能够计算出沿结构生长方向的介电常数分量。有了这些数据，人们可以确定负折射发生的条件，并计算结构的折射率值，以及在预定义的总电子片密度下结构表现负折射的频率范围。
In order to avoid losses in metamaterial unit cells at frequencies of interest, caused by metallic inclusions, an active medium design has been proposed. As candidate structures for this active medium, we have chosen quantum cascade lasers because of their high output gain. Here we analyze and compare two quantum cascade structures that emit at 4.6 THz and 3.9 THz, respectively, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all relevant Landau levels, and obtain the necessary information about carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure. With these data one can determine the conditions under which negative refraction occurs, and calculate the values of the refractive index of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.