Interaction of high power laser beam with magnetized plasma and THz generation

Abstract

This paper presents an investigation of the excitation of a Tera hertz (THz) radiation by nonlinear interaction of a circularly polarized high power laser beam and density ripple in collisionless magneto plasma. The ponderomotive force due to the nonlinear interaction between the laser and density ripple generates a nonlinear current at a difference frequency. If the appropriate phase matching conditions are satisfied and the frequency of the ripple is appropriate, then this difference frequency can be brought in the THz range. Filamentation (self focusing) of a circularly polarized beam propagating along the direction of ambient magnetic field in plasma is first investigated within paraxial ray approximation. The beam gets focused when the initial power of the laser beam is greater than its critical power. Resulting localized beam couples with the pre-existing density ripple to produce a nonlinear current driving the THz radiation. Analytical expressions for the beam width of the laser beam, electric vector of the THz wave have been obtained. By changing the strength of the magnetic field, one can enhance or suppress the THz emission. For typical laser beam and plasma parameters with the incident laser power flux = 10 14 W/cm 2 , laser beam radius (r 0 ) = 40 μm, laser frequency (ω 0 ) = 10 14 rad/s and plasma density (n 0 ) = 3 × 10 18 cm −3 , normalized ripple density amplitude (μ) = 0.3, the produced THz emission can be at the level of Giga watt in power.

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

“…Currently, the powerful sources of THz radiation are large accelerator-based sources and the lack of compact high-power sources limits the exploitation of full potential of THz radiation. For the development of practical high-power THz sources, schemes based on laser-plasma interaction have been proposed (Hamster et al, 1993;Yugami et al, 2002;Gildenburg & Vvedenskii, 2007;Sharma et al, 2010;Jha et al, 2011;. Filamentation (phenomena of periodic self-focusing and defocusing) is another process from which THz can be generated.…”

Strong terahertz radiation generation by beating of two x-mode spatial triangular lasers in magnetized plasma

“…In this scheme, magnetic field plays two roles (1) it controls the phase velocity and group velocity of beating lasers and (2) the polarization of generated THz wave (Sharma et al, 2010). Triangular envelop of x-mode laser beams is utilized to enhance beat ponderomotive force acting on plasma electrons.…”

Surface wave excitation by a density modulated electron beam in a magnetized dusty plasma cylinder

“…It can be excited by an electron beam (Liu & Tripathi, 2000;Prakash & Sharma, 2009;Girka et al, 2011a;2011b), by an ion beam (Girka et al, 2011a;2011b), by attenuated total reflection (ATR) configuration (Kretschmann & Raether, 1968;Kretschmann, 1971;Fink & Schneider, 1975), by ripples of suitable wave number over the metallic interface (Liu & Tripathi, 2000), by light via prism coupling (Chen et al, 2011), or by laser (Anisimov et al, 1988;Parashar et al, 1998;Bouhelier et al, 2007). The interaction of laser beam with plasma eigenmodes is also an important area of research (Ghorbanalilu, 2012;Verma & Sharma, 2011;Sharma et al, 2010;Saini & Gill, 2006;Anderson et al, 2005;Paknezhad & Dorranian, 2011) in recent years.…”