Resonant terahertz generation from laser filaments in the presence of static electric field in a magnetized collisional plasma

Abstract

A new scheme of terahertz (THz) generation from laser filaments in plasma in the presence of static electric and magnetic fields is proposed. Two femtosecond laser pulses of different frequencies ($\omega_{1} ,\omega_{2}$) and wave numbers ($k_{1} ,k_{2}$) are co-propagating under the action of filamentation in a magnetized collisional plasma. THz wave is generated due to the nonlinear coupling between nonlinear velocity and electron density in magnetized collisional plasma. For suitable laser and plasma parameters, the nonlinear coupling results in enhanced nonlinear current density which leads to resonant THz waves. The external D.C. electric and magnetic fields are applied perpendicular to each other and mutually perpendicular to the direction of co-propagating lasers. We have obtained the expression of a dielectric tensor with anisotropic nature, and it is found very useful in the study of THz generation. The applied magnetic field also aids to enhance the transverse components of nonlinear current. This nonlinear current is responsible to generate enhanced terahertz waves at frequency ($\omega_{1} - \omega_{2}$). We have found that the normalized THz amplitude increases significantly with the increase in applied D.C. electric field from 10 to 30 kV/cm and magnetic field from 10 to 50kG. Our scheme with numerical analysis may open the door for efficient and cost-effective way to generate THz radiation.