munther baqir hassan alkhqani

In this article, the plasma density, the laser intensity and the external magnetic feld are playing vast roles frstly to generate a coherent THz wave then to enhance the stability of generated THz. Due to the relativistic increase of electron mass, the relativistic self-focusing of a right circular polarized (RCP) laser beam inside magnetized plasma will occur which leads to raising the laser power to enough limits for exciting the terahertz wave. By fulflling the energy–momentum conservation conditions, a terahertz wave frequency at the diference between the laser pump wave frequency and plasma wave frequency is obtained. More stabilization and higher power (reaching to tens of gigawatts) of terahertz feld amplitude have been observed whenever the plasma density, the laser intensity, and the external magnetic feld are increased. Better results are recorded at high THz frequency (5 THz) compared with low THz frequency (1 THz).

The filamentation instability (self-focusing) of laser beam propagating through magnetized plasma is occurring under the effect of nonlinear relativistic force. Taking into account the nonparaxial ray approximation, the laser beam of initial intensity (I ∼ 1019 W/cm2) is interacting with collisionless plasma to excite a positive lens that is leading to self-focus of the laser beam. The longitudinal static magnetic field is playing a significant role for increasing the self-focusing behavior of laser beam. The numerical results demonstrated that the self-focusing of the nonparaxial laser beam was lower than that of the paraxial laser beam.

In this article, the relativistic nonlinear self-focusing of a right circular polarized laser beam propagated through magnetized plasma was investigated. The high power of laser beam which resulted from the self-focusing effect was exploited to excite an electromagnetic wave to the terahertz frequency range. By controlling the external longitudinal magnetic field, a high stabilized terahertz field was observed. At terahertz frequency (1THz) where the initial laser beam radius and initial laser beam intensity , the highest terahertz radiation power attained was about tens of gigawatts that associated with best stabilization seen.