An alternative approach is proposed to improve the conventional (based on the low-temperature grown GaAs and Si-doped GaAs superlattice) photoconductive antenna (PCA) performance by modification of the planar electrodes design and crystallographic orientations of the GaAs substrate ((100) and (111)-A). The electrode scheme design includes a combination of logarithmic spiral, bow-tie, and plasmonic antennas and results in appearance of sharp resonant peaks, high spectral bandwidth and high signal-to-noise ratio, and significant enhancement of the output terahertz (THz) power. The material design leads to significant increase in the THz output power (by 6.4 in GaAs (100), by 5.6 in GaAs (111)-A PCAs) regarding to a conventional antenna. The substrate crystallographic cut direction influences the relaxation time constant of photoexcited charge carriers being an order of magnitude smaller in the sample grown on the GaAs (111)-A than in the one on the GaAs (100). The simulation model supports experimental results demonstrating that the optimal period of the plasmonic antenna grid providing the highest efficiency of THz radiation generation, is about 200 nm. Comparison of the THz spectra in manufactured antennas against the conventional stripline PCA shows a broadening band toward the low-frequency region down to 0.1 THz with a resonance at 0.2 THz.

中文翻译：

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GaAs衬底晶体取向和等离子栅周期对太赫兹天线性能的影响

提出了一种替代方法，通过修改 GaAs 衬底 ((100) 和(111)-A)。电极方案设计包括对数螺旋天线、蝴蝶结天线和等离子体天线的组合，导致出现尖锐的谐振峰、高光谱带宽和高信噪比，并显着增强了输出太赫兹 (THz) 功率. 与传统天线相比，材料设计导致 THz 输出功率显着增加（GaAs (100) 增加 6.4，GaAs (111)-A PCA 增加 5.6）。衬底晶体学切割方向影响光激发电荷载流子的弛豫时间常数，在 GaAs (111)-A 上生长的样品比在 GaAs (100) 上生长的样品小一个数量级。仿真模型支持实验结果，证明提供最高太赫兹辐射生成效率的等离子体天线网格的最佳周期约为 200 nm。制造天线中的太赫兹频谱与传统带状线 PCA 的比较显示了一个向低频区域扩展的频带，低至 0.1 太赫兹，谐振频率为 0.2 太赫兹。仿真模型支持实验结果，证明提供最高太赫兹辐射生成效率的等离子体天线网格的最佳周期约为 200 nm。制造天线中的太赫兹频谱与传统带状线 PCA 的比较显示了一个向低频区域扩展的频带，低至 0.1 太赫兹，谐振频率为 0.2 太赫兹。仿真模型支持实验结果，证明提供最高太赫兹辐射生成效率的等离子体天线网格的最佳周期约为 200 nm。制造天线中的太赫兹频谱与传统带状线 PCA 的比较显示了一个向低频区域扩展的频带，低至 0.1 太赫兹，谐振频率为 0.2 太赫兹。