To undertake THz spectroscopy and imaging, and accurately design and predict the performance of quasi-optical components, knowledge of the parameters of the beam (ideally Gaussian) emitted from a THz source is paramount. Despite its proliferation, relatively little work has been done on this in the frame of broadband THz photoconductive antennas. Using primarily pinhole scanning methods, along with stepwise angular spectrum simulations, we investigate the profile and polarization characteristics of the beam emitted by a commercial silicon-lens-integrated THz photoconductive antenna and collimated by a TPX (polymethylpentene) lens. Our study flags the limitations of the different beam profiling methods and their impact on the beam Gaussianity estimation. A non-Gaussian asymmetric beam is observed, with main lobe beam waists along x and y varying from 8.4$\,\pm\,$0.7 mm and 7.7$\,\pm\,$0.7 mm at 0.25 THz, to 1.4$\,\pm\,$0.7 mm and 1.4$\,\pm\,$0.7 mm at 1 THz, respectively. Additionally, we report a maximum cross-polar component relative to the on-axis co-polar component of $-$11.6 dB and $-$21.2 dB, at 0.25 THz and 1 THz, respectively.

中文翻译：

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商用镜头辅助太赫兹时域光谱仪的光束分析

为了进行太赫兹光谱和成像，并准确设计和预测准光学组件的性能，了解从太赫兹源发射的光束（理想情况下为高斯）的参数至关重要。尽管其扩散，但在宽带太赫兹光电导天线框架中的工作相对较少。主要使用针孔扫描方法以及逐步角光谱模拟，我们研究了由商用硅透镜集成太赫兹光电导天线发射并由 TPX（聚甲基戊烯）透镜准直的光束的轮廓和偏振特性。我们的研究指出了不同光束分析方法的局限性及其对光束高斯估计的影响。观察到非高斯非对称光束，主瓣束腰沿X 和 是 从 8.4 变化$\,\pm\,$0.7 毫米和 7.7$\,\pm\,$在 0.25 THz 时为 0.7 毫米，至 1.4$\,\pm\,$0.7 毫米和 1.4$\,\pm\,$1 THz 时分别为 0.7 mm。此外，我们报告了相对于上- 轴共极分量 $-$11.6 分贝和 $-$21.2 dB，分别为 0.25 THz 和 1 THz。