Research on non-equilibrium state of driving materials and devices for ultra-fast high intensity laser pumping terahertz source (2000-2023)

Terahertz source is the foundation of Terahertz science and technology development and related application research. Ultrafast laser provides a stable and reliable excitation source for terahertz generation and detection. Terahertz waves can be generated by ultrafast laser pumping various excitation media, such as solid media, such as photoconductive antennas, crystals, etc. A gaseous medium, such as air; Liquid media, such as liquid water, liquid gallium, liquid nitrogen, etc. Plasma media, such as titanium film, metallic copper foil. With the further increase of terahertz field intensity, the strong field terahertz interaction with matter and terahertz nonlinear spectroscopy were born. Furthermore, we have shown that not only the terahertz spectroscopy could help to reveal the excited state dynamics in solids, but the terahertz emission spectroscopy could also help to distinguish the strong coupling of the carriers, excitons, phonons and other elementary excitations. In this paper, the development of terahertz source generated from four different types of media excited by ultrafast laser is reviewed, including its working principle and existing problems. The current applications of strong field terahertz wave in physical state regulation are summarized. Finally, the future development trend and application prospect of terahertz source are prospected.