This work presents a brief review of our recent research on an antiresonant mechanism named core antiresonant reflection (CARR), which leads to a broadband terahertz (THz) spectrum output with periodic dips at resonant frequencies after its transmission along a hollow-core tubular structure (e.g., a paper tube). The CARR theory relies only on parameters of the tube core (e.g., the inner diameter) rather than the cladding, thus being distinct from existing principles such as the traditional antiresonant reflection inside optical waveguides (ARROWs). We demonstrate that diverse tubular structures, including cylindrical, polyhedral, spiral, meshy, and notched hollow tubes with either transparent or opaque cladding materials, as well as a thick-walled hole, could indeed become CARR-type resonators. Based on this CARR effect, we also perform various applications, such as pressure sensing with paper-folded THz cavities, force/magnetism-driven chiral polarization modulations, and single-pulse measurements of the angular dispersion of THz beams. In future studies, the proposed CARR method promises to support breakthroughs in multiple fields by means of being extended to more kinds of tubular entities for enhancing their interactions with light waves in an antiresonance manner.

为深入了解金属弹簧波导对太赫兹波的传输效果，对不同螺线间距金属弹簧的太赫兹波传输特性进行了实验研究。实验结果表明，对于线径0.8 mm、外直径12 mm、长14 cm的金属弹簧，在3.5/4.4 mm等较大的螺距下，弹簧波导反而能在较大的带宽下传导太赫兹波，并具有良好的偏振保持能力。3.5/4.4 mm螺距弹簧的太赫兹传输带宽均约为0.9 THz，且在其峰值频率处的传输损耗分别约为0.2 cm⁻¹和0.27 cm⁻¹。此外，金属弹簧能将太赫兹模式束缚在空气芯内传输，而非通过金属螺线导引传输。该研究结果对金属弹簧波导在太赫兹技术中的应用具有一定参考意义。

针对固体、液体不同形态易燃易爆危险物品准确识别的要求，设计并搭建了多组件太赫兹时域波谱仪。用该波谱仪检测了两种不同形态的易燃易爆危险品。测试结果表明，该波谱仪在0.1～2 THz频谱范围内检测危险品时都能得到明显的特征吸收峰，因此可以使用该波谱仪识别不同形态的危险品，并为公共安全检查提供一种新的方法。

In this work, it has been demonstrated that in order to fully understand the terahertz (THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric (1DND) waveguide model. By combining the 1DND model with the conventional four-wave mixing (4WM) and photocurrent (PC) models, the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC processes, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.