A strong-field THz light source based on coherent transition radiation

Abstract

Terahertz (THz) radiation is a powerful tool for exploring various scientific frontiers through THz pump–probe experiments. However, different experiments may require THz radiation with different spectral properties, such as broad-band or narrow-band, which are difficult to be generated by a single light source. In this paper, we propose a THz light source that can produce both types of THz radiation by manipulating the longitudinal profile of an electron beam and exploiting coherent transition radiation. We perform theoretical analysis and numerical simulations based on the parameters of the Shanghai soft X-ray Free-Electron Laser facility, and the results show that the proposed light source can generate broad-band THz radiation with a pulse energy of 342 µJ and narrow-band THz radiation with a pulse energy of 91 µJ. The proposed light source can offer more flexibility and versatility for free-electron laser (FEL) users to conduct THz pump–probe experiments.

A strong-field THz light source based on coherent transition radiation at the Shanghai soft x-ray free-electron laser facility

“…Then, the accelerated electron beam is modulated by an external frequency beating laser pulse. Compared with our previous method 21 , an ultra-short electron beam for generating broadband THz radiation is obtained through frequency beating laser compression. In addition, an electron bunch train used to generate narrowband THz radiation is also obtained through frequency beating laser modulation.…”

“…where N is number of the electrons and 𝐹(𝑘, 𝜎 𝑧 ) = |∫ 𝑒 𝑖𝑘𝑧 𝑆(𝑧, 𝜎 𝑧 ) 𝑑𝑧| 2 is the form factor of the electron beam. According to equation ( 4), the angular distribution or energy spectrum distribution of CTR can be easily obtained by integrating the radiation wave number k or the solid angle 𝛺 respectively 21 .…”