Generation of mode-locked EUV and soft X-ray radiation via coherent Thomson scattering from a density-modulated electron bunch

摘要: Mode-locked laser frequency combs underpin precision measurements and ultrafast science. However, their applications in short wavelengths are limited by gain bandwidth and wavelength coverage. In this work, a compact scheme for generating coherent radiation in the EUV and soft X-ray range with a comb-like spectrum based on the head-on collision between a density-modulated relativistic electron beam with an intense long-wavelength Gaussian laser is proposed. A theoretical analysis of the spectral structure is developed and validated by numerical simulations. Our simulations numerically reproduce the spectral positions, spacings, and number of comb lines, showing that frequency combs can be realized without conventional optical cavities or electron-beam delay lines. The distribution of periodically microbunched electron slices leads to the formation of ultrashort pulse trains with stable temporal spacing. These results demonstrate a viable route toward coherent EUV and soft X-ray frequency comb sources, thereby providing new opportunities for compact and tunable platforms in ultrafast science and precision spectroscopy.