THz generation by cosh-Gaussian lasers in a rippled density plasma

Abstract

This paper presents a scheme to achieve THz radiation by the beating of cosh-Gaussian lasers in spatially periodic density plasma (ripple density). Here, the lasers exert a nonlinear ponderomotive force along the transverse direction which imparts an oscillatory velocity to electrons that couples with the density ripple to generate a stronger transient transverse current due to the spatial variation of their fields, driving THz radiation. The importance of laser-beam-width parameters, decentred parameter, amplitude and periodicity of the density structure are discussed for THz emission. By changing the decentred parameter the peak intensity of lasers can be shifted in the transverse direction and a notable change is found in the magnitude of THz field amplitude and its conversion efficiency.

THz radiation by amplitude-modulated self-focused Gaussian laser beam in ripple density plasma

“…The role of density ripple in the plasma in THz generation has been discussed by several researchers Singh et al, 2013). The importance of density ripple in the plasma has also been discussed by some authors in context of other phenomena taking place in the laser-plasma interaction (Singh et al, 2010;Xia & Xu, 2013;Xia, 2014).…”

“…have been used to generate THz Singh et al, 2013). As the propagation and focusing properties of Gaussian laser beam in plasma have been studied extensively (Sodha et al, 1974;1979), it is one of the most preferred beam profiles used in laser-plasma interaction studies.…”

“…Because of the variation in intensity in the direction transverse to the laser propagation, a component of ponderomotive force is exerted on electrons, which gives rise to a stronger transient current driving THz radiation. The ripple in plasma density provides the necessary condition for phase matching (Singh et al, 2013) and plays the main role for the extraction of THz radiation. In the absence of ripple density, the THz cannot be generated by the present scheme.…”

Generation of terahertz radiation via cosh‐Gaussian and top‐hat laser beams in a collisional magnetized plasma

“…[48] Vacuum electronic sources include the backward-wave oscillator, [49,50] extended-interaction klystrons, [51,52] travelling-wave tubes, [53] and synchrotrons. [66] Varshney et al have proposed THz radiation by beating of two cosh-Gaussian lasers in a rippled density plasma in the presence of a transverse static magnetic field. [58,59] Frequency multipliers are used to fundamentally shift sub-THz electronic oscillations into the THz range.…”

“…[62,63] Another way to generate THz radiation is to use semiconductor superlattice. [73] Many cited references [30,31,38,[65][66][67] study THz radiation generation by beating of two laser beams by applying a perpendicular magnetic field to the laser beams' propagation direction to achieve higher efficiency than if they have used different laser beam profile. [65] Singh et al have reported THz generation by mixing two cosh-Gaussian laser beams in a density rippled plasma.…”