Magnetic-induced conversion between electric quadrupole radiation and quasi dipole radiation at THz band

Based on Particle-in-Cell simulation and theoretical analysis, we demonstrate the possibility of the realization of the electric quadrupole radiation (EQR) and the quasi dipole radiation (QDR) modes at the THz band from the electrostatic oscillation of the electrons driven by the two color lasers inside the plasma. Interestingly, an implantation of the external magnetic field will induce the flexible conversion between the EQR mode and the QDR mode. The emission angle, radiation frequency, and radiation field strength of the two radiation modes can be highly modulated by adjusting the intensity of the magnetic field, the frequency of the laser pulses, and the density of the plasma. This provides a new and practical way towards the generation and conversion of the multiple radiation modes, greatly extending the potential for optical manipulation in magnetized plasma.