Terahertz Radiation Generation by Beating two Obliquely Incident Lasers on a Plasma with Density Gradient

Terahertz excitation by beating two collinear lasers, propagating at an angle to density gradient in plasma, is investigated. The lasers exert a ponderomotive force on electrons that creates beat frequency current density (J) over arrow(NL) with del x(J) over arrow(NL) not equal 0. This excites electromagnetic radiation. For a parabolic density profile with density peak slightly less than the critical density, the beat wave amplitude acquires large values near the density peak and saturates.