This research uses a two-dimensional photocurrent model to propose and theoretically demonstrate an effective method for generating polarization-controllable terahertz wave from gaseous plasma according to experimental conditions. The simulation results show that in a combined field composed of a linear two-color laser field of 1600 nm+800 nm and a third circularly polarized laser pulse, the phase of the third pump laser is the key factor to control the polarization of the THz wave generated by the emitted air plasma. Theoretical simulation also shows that based on the two-color field, by selecting the appropriate available laser wavelength for the third pulse, the terahertz output can be effectively increased, and the terahertz conversion efficiency is significantly improved, which improves the production efficiency of the lasers. For such an incommensurate three-color femtosecond laser field, the intensity ratios of the fundamental beam and the third laser can also be used to control the polarization state and the direction of the terahertz radiation. Using current laser technology, our scheme can be implemented in experiments.
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