Collimation and monochromaticity of γ-rays generated by high-energy electron colliding with tightly focused circularly polarized laser with varied intensities

The collision of high-energy electron and laser pulses produces nonlinear inverse Thomson scattering, which can generate gamma-rays. We study the effect of laser intensity on the energy angular distribution and spectrum of gamma-ray radiation in tightly focused pulses. The gamma-rays at non-relativistic intensity have good collimation and monochromaticity, and the radiation energy increases with the laser intensity. The 'jumping point' phenomenon of radiation energy variation under relativistic intensity and the 'black hole' of energy angular distribution were discovered. As the laser intensity increases, there is a red shift in the radiative harmonic spectrum. And at relativistic intensity, supercontinuum (tunable) gamma-rays can be obtained. These findings help us use NITS for optical research.