Enhance terahertz radiation and its polarization- control with two paralleled filaments pumped by two-color femtosecond laser fields.

We present experimentally an obvious enhancement of the terahertz (THz) radiation with two paralleled filaments pumped by two-color laser fields for a full use of a high laser power, compared with single filament. By mapping the 3-dimensional electric trajectories of generated THz fields with a (111) ZnTe crystal, we observe that the total THz polarization from two filaments can be manipulated by varying the time delay between the two orthogonally polarized pumps, which agrees well with the simulations under the photocurrent model. Notably, the power and spectrum of the THz field almost keep unchanged while manipulating the ellipticity of the THz polarization, which is important for a polarization-controllable THz source.