Study Of Mechanisms For THz Radiation Produced By Laser Wakefields

The generation and application of Terahertz(THz,10¹² Hz) radiation have been attracting continued interest.The thesis studied on the mechanism of generating ultra-intense THz emission,by the interaction between short intense laser pulse and the plasma,through the linear mode conversion.Based on the theory of the laser-plasma interaction,the necessary condition for generation of linear mode conversion was analyzed:the dispersion relation of plasma wave (ω²=ω_p²+3k²v²) matched with the dispersion relation of electromagnet wave (ω²=ω_p²+k²c² ).The conversion efficiency of the plasma wave to electromagnetic radiation is calculated to be around 50%.One-dimensional and two-dimensional particle-in-cell simulation are performed;the spatial-temporal diagram of laser wakefield emission,the emission spectrum diagram of plasma density profiles in linear and experiential state,and other associated diagrams are obtained.The results show that the induced emission power can be as large as MV and a fewμJ in the energy.