Controlling Amplitude and Radiation Pattern of Emitted Terahertz by Group Velocity Mismatch

In this paper, the effect of group velocity mismatch on the characteristic of terahertz (THz) radiation from a plasma irradiated by two-color laser pulses is investigated. The group velocity mismatch is directly related to the slippage-limited interaction length (SLIL). In order to control the characteristic of generated THz radiation, the SLIL effect on the radiation pattern and electric field amplitude is investigated. The SLIL can be controlled by the background plasma density. By rising the plasma density, the SLIL is decreased. Consequently, the THz electric field amplitude is reduced, and the radiation pattern is modified. In addition, by tuning the plasma density, the power pattern directivity and the sidelobe level are controlled.