Third Harmonic Generation of q-Gaussian Laser Beam in Collisional Plasma

Third harmonic generation (THG) of q-Gaussian laser beam in Collisional plasma is examined in present investigation. In such plasma, non-uniform heating gives rise to collisional nonlinearity, which redistributes plasma carriers and induces density gradients inside plasma. These density gradients excite electron plasma wave (EPW) at twice fundamental wave frequency through V⃗ × B⃗ force. This EPW couples with fundamental wave thereby causing production of THG. Using WKB and paraxial approach, a nonlinear ODE governing beam waist evolution of fundamental wave, along with conversion efficiency of 3rd harmonics are derived. Furthermore, effects of key laser-plasma parameters on self-focusing of fundamental wave and third harmonic conversion efficiency are systematically analyzed.