Enhanced terahertz generation via plasma modulation on two bunches

Terahertz (THz) radiation finds important applications in various fields, making the study of THz sources significant. Among different approaches, electron accelerator-based THz sources hold notable advantages in generating THz radiation with narrow bandwidth, high brightness, high peak power, and high repetition rate. To further improve the THz radiation energy, the bunching factor of the free electron bunch train needs to be increased. We propose and numerically reveal that, by adding an additional short-pulse drive beam before the main beam as the excitation source of nonlinear plasma wake, the bunching factor of the main beam can be further increased to ∼0.94, even though with a relatively low charge, low current, and relatively diffused electron beam. Two such electron beams with loose requirements can be easily generated using typical photoinjectors. Our work provides a way for a new THz source with enhanced radiation energy.