We propose a scheme for the generation of terahertz (THz) radiation in a plasma by beating of two flat-topped laser beams when a static magnetic field is applied to the plasma with a parallel or perpendicular direction. We show that the presence of a static magnetic field can enhance drastically the power and efficiency of THz radiation. The power and efficiency enhancement of the perpendicular magnetic field is greater than that of parallel one. Furthermore, the perpendicular magnetic field produces THz radiation with a square shaped field profile which has many applications in industries especially in optical communication. Optimizing the laser beams and magnetized plasma parameters and considering the interaction (mutual effect) between laser beams, THz radiation, and plasma, the THz radiation efficiency up to 8.3% can be obtained. A comparison between the THz radiation generated by flat-topped and super Gaussian laser beams shows that, at the same conditions, the THz radiation generated by flat-topped beam lasers has some advantages such as about two times wider flat-topped region and more than two times higher efficiency.

In the present paper, a scheme for generation of terahertz (THz) radiation in electron-neutral collisional plasma based on beating of two Gaussian laser array beams has been proposed. It is shown that the efficiency of THz radiation based on the Gaussian laser array beams can be enhanced drastically in comparison with the efficiency of THz radiation based on the Gaussian one. Furthermore, the producing THz radiation by the Gaussian laser array beams, which has an exclusive field profile, is affected by some array structure parameters. It can also be used to overcome the negative consequences of electron neutral collisions in plasma, which may be occurring in the THz radiation generation process. Optimizing the collisional plasma, laser beams and array structure parameters, THz radiation efficiency up to 0.07% can be obtained in our scheme which is about three times greater than the maximum efficiency obtained for standard (single) Gaussian laser beam. Also, considering the electrostatic energy channel in solving the THz wave equation, and reduction of THz radiation efficiency to 0.054%, in this assumption, the ratio between the efficiency of Gaussian laser array beams and standard Gaussian laser beam remained unchanged.

This paper presents a scheme of terahertz radiation generation based on beating of two dark hollow laser beams with different frequencies, the same electric field amplitudes, in actual plasma with spatially periodic density that electron–neutral collisions have taken into account. The main feature of considered hollow laser beams is, having the same power at different beam orders. Because of special distribution in beam intensity gradient in dark hollow laser beam, the produced terahertz radiation has special field profile. The effects of laser and plasma parameters on terahertz radiation generation are investigated analytically. It can be deduced that by increasing beating frequency, efficiency of terahertz generation decreases which can be compensated by manipulating density ripple magnitudes and dark-size adjusting parameter. The intensity of the emitted radiations is found to be highly sensitive to the beam order. Based on the results of this paper, optimization of laser and plasma parameters can increase the efficiency of terahertz radiation generation strongly.

A scheme of terahertz (THz) radiation generation is proposed by beating of two spatial-triangular laser beams in plasma with a spatially periodic density when electron–neutral collisions have taken into account. In this process, the laser beams exert a ponderomotive force on the electrons of the plasma and impart the oscillatory velocity at the difference frequency in the presence of a static magnetic field which is applied parallel to the direction of the lasers. We show that higher efficiency and stronger THz radiation are achieved when the parallel magnetic field is used to compare the perpendicular magnetic field. The effects of beam width of lasers, collision frequency, periodicity of density ripples, and magnetic field strength are analyzed for strong THz radiation generation. The THz field of the emitted radiations is found to be highly sensitive to collision frequency and magnetic field strength. In this scheme with the optimization of plasma parameters, the efficiency of order 21% is achieved.

Terahertz (THz) radiation generation by nonlinear mixing of two laser beams, obliquely incident on an overdense plasma is investigated. In an overdense plasma, the laser beams penetrate to only thin layer of a plasma surface and reflected. At this thin layer, the laser beams exert a ponderomotive force on the electrons of plasma and impart them oscillatory velocity at the different frequency of lasers. THz waves appear in the reflected component from the plasma surface. The amplitude of THz waves can be augmented by applying the magnetic field perpendicular to the direction of propagation of lasers. It is found that the field strength of the emitted THz radiations is sensitive to the angle of incident of the laser beams, beat frequency, and magnetic field strength. In this scheme, the magnetic field strength plays an important role for strong THz wave generation.