PIC Simulation On The THz Radiation Excited From The Interaction Between Multiple Laser Pulses And Plasma

With the rapid development of research on the THz wave and its application, we are in urgent need of a high power, tunable easily THz radiation source. Recently, Zheng-Ming Sheng, a research fellow from Institute of Physics, CAS, presented a new theory called Linear Mode Conversion to get a powerful THz radiation, which carved out a new way for us to get a new pattern radiation source.Based on the research by Zheng-Ming Sheng, We conduct numerical simulations on the THz radiation excited from the laser-plasma interaction by using a 2D3V PIC code and investigate the effects of laser parameters on the THz radiation power and frequency in contrast to the results from the Linear Mode Conversion theory. The PIC simulation results show that the laser pulse intensity has a dominating impact on the THz radiation power; the optimal pulse width exciting the strongest electrostatic wave and THz radiation is around the plasma wavelength. Meanwhile, there is an optimal focused radius which is around0.35λ_po for the strongest radiation and the radiation frequency decreases with the increase ofthe focused radius. Our simulation results agree with the Linear Model Conversation theory perfectly.Multiple laser pulses could not only increase the amplitude of the electrostatic wave effectively, but also suppress the increase of plasma instability. So we present a new approach to increase the THz radiation by using multiple laser pulses for the first time. The results show that the laser with four pulses could strengthen the THz radiation obviously. By using multiple laser pulses scheme, we obtain a THz wave with a pulse width of 300 fs, an energy of 1μJ and radiation power up to 7.16 MW which is six times of that from a single laser purse scheme. Furthermore, the results also show that an optimum pulse interval for the strongest radiation is equal to the plasma wave length. Our simulation results prove that the multiple laser pulses scheme could enhance the THz radiation power greatly, which is valuable to the research on the THz theory and its application in the future.