We propose a novel optical spatial differentiator to perform the differentiation computation in terahertz region based on the graphene metalines, which consist of graphene layers with different widths and chemical potentials. The numerical simulation results show that when beam waist size w>1.9λ, the metalines perform the first-order differentiation in the reflection spectrum with efficiency>97%, which can be theoretically demonstrated by using transfer matrix method. In order to further improve the performance of the differentiator, evolutionary algorithm, such as genetic algorithm, is used to inversely design the structure parameters and chemical potentials of graphene metalines. The optimization results show that some performance metrics of the differentiator, for example normalized root-mean-square deviation, are better than the previous structures. Obviously, the proposed graphene metalines combined with inverse design technology can achieve a high-performance optical spatial differentiator in terahertz region and provide a new way to design the photonics devices.

中文翻译：

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基于石墨烯金属线和进化算法的高效光学空间一阶微分器

我们提出了一种新的光学空间微分器，以基于石墨烯金属线在太赫兹区域执行微分计算，石墨烯金属线由具有不同宽度和化学势的石墨烯层组成。数值模拟结果表明，当束腰尺寸w>1.9λ时，金属线在反射光谱中进行一阶微分，效率>97%，这可以通过传递矩阵法进行理论证明。为了进一步提高微分器的性能，采用遗传算法等进化算法对石墨烯金属线的结构参数和化学势进行逆向设计。优化结果表明微分器的一些性能指标，例如归一化均方根偏差，比以前的结构更好。显然，所提出的石墨烯金属线结合逆向设计技术可以在太赫兹区域实现高性能的光学空间微分器，为设计光子器件提供了一种新方法。