研究了焦点位置附近太赫兹波的横模分布,目的在于了解系统中太赫兹波的横向分布情况,为进行太赫兹光谱和成像实验提供依据。 通过太赫兹波逐点扫描成像,对经常被用来放置测试样品位置附近的太赫兹波横模分布情况进行了定性的分析。利用“狭缝法"测量了太赫兹光束的束宽。结果表明,太赫兹波在焦点附近不同位置的横向分布有较大差异,在焦点处对应于最长波长1.5 mm的最小光斑直径约为1.0 mm,这说明太赫兹波的聚焦有一定的限度。实验确定了系统中放置样品的最佳位置,对开展太赫兹光谱和成像研究有参考价值。

The transverse mode distribution of THz wave near the position of focus point was studied in this paper. It is important to know the transverse distribution of THz wave, which can be referenced as an evidence of sample positioning in THz spectroscopy and THz imaging experiments. By using THz point-by-point imaging technology, THz transverse mode distribution in the positions, where samples are usually placed, is analyzed qualitatively. By applying “slit method”, the beam width of THz wave was measured. The results show that the shapes of the transverse modes of THz wave in different positions around the focus have much difference. To the maximum wavelength of about 1.5 mm of THz wave in the system, the minimum diameter of THz beam at the focus point is around 1.0 mm. The results provide a basic reference for further application of THz Spectroscopy and THz Imaging.