Terahertz to near infrared radiation generation using two-colour counter and co-polarized laser pulses propagating in homogeneous plasma

Abstract

This study deals with the generation of terahertz (THz) to near infrared (NIR) radiation fields using two-colour linearly polarized copropagating laser pulses having either counter or co-polarization state. The frequency difference between the two laser pulses is considered to be integral multiple of the plasma frequency. Perturbation technique and quasistatic approximation have been used to obtain radiation field equations. Analytical and two-dimensional particle in cell simulation studies of the proposed configuration show that the transverse and axial plasma electron velocities arising due to nonlinear coupling of the two pulses are responsible for generation of off-axis linearly polarized radiation fields which propagate through plasma into vacuum. The frequency of generated radiation is ∼40 THz (∼60 THz), when the frequency difference of the laser pulses is two (three) times the plasma frequency. Analytical results are validated using VSim particle in cell simulation code.