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^NL with V×J^NL ≠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.