Challenge of new extreme material science using high-energy THz source

我们利用超短、强激光脉冲和脉冲放电产生的可控等离子体，演示了台式太赫兹电磁波源和极紫外光源。太赫兹辐射可以由激光产生的电离前沿产生的突发电流产生，该电离前沿在静电场的诱导下在空气中产生光场诱导的电离。实验结果与计算结果相似，太赫兹辐射的电场幅值随外加电场电压的增加而增加。我们还演示了一种基于纯钾蒸气的放电产生的微等离子体极紫外源。钾离子产生40nm左右的强宽带发射，带宽为8nm[半最大全宽（FWHM）]。微放电的电流-电压特性表明源工作在空心阴极模式下。通过与原子结构计算的比较，发现宽带发射主要是由于钾离子在K^<2+>到K^<4+>范围内的3d-3p跃迁。

We have demonstrated table top terahertz electromagnetic wave source and extreme ultraviolet light source by using a controlled plasma produced by an ultrashort, intense laser pulse and pulse discharge. The terahertz radiation can be generated by the burst current produced by a laser created ionization front, which is induced an optical-field-induced ionization in air with a static electric field. The experimental results behave similarly to calculated results, and electric field amplitude of THz radiation increase with increase in applied voltage of a static electric field. We also have demonstrated a discharge-produced microplasma extreme ultraviolet source based on a pure potassium vapor. Potassium ions produced strong broadband emission around 40nm with a bandwidth of8 nm [full width at half-maximum (FWHM)]. The current-voltage characteristics of microdischarge suggest that the source operates in a hollow cathode mode. By comparison with atomic structure calculations, the broadband emission is found to be primarily due to 3d-3p transitions in potassium ions ranging from K^<2+> to K^<4+>.