Particle-in-cell simulation for frequency up-conversion of microwave to terahertz radiation by a relativistic hollow ionization front

The interaction of an electromagnetic wave with a relativistic ionization front with frequency up-conversion has been demonstrated by the particle-in-cell (PIC) method. In the PIC simulation, the plasma ionization front is formed by using an electron beam ionizing the background gas. The PIC results are in good agreement with the basic analytic theory. In addition, the charged particles are modulated in the interaction area observed in the PIC simulation, which is hardly obtained by other methods. Based on the verified PIC methods, a relativistic hollow ionization front for frequency up-conversion of microwave to terahertz radiation is proposed for increasing the reflection cross section. Finally, the reflected energy can be increased by at least 3 orders of magnitude compared to the traditional methods.