THz Generation in Plasma: A Comparative Study of q-Gaussian, Sech, and Super-Gaussian Laser Pulses

This research offers a complete analytical and numerical examination of terahertz (THz) generation in collisional homogeneous plasma caused by different laser beam profiles q-Gaussian, sech-Gaussian, and super-Gaussian pulses. Through the closed-form expressions of the nonlinear ponderomotive force and the plasma current density that they derive, as well as the THz electric field that results, the authors systematically evaluate the influence of THz conversion efficiency by the beam-shaping parameters q, b, and p for the normalized frequency range of 1.05 ≤ ω/ω p 1.20. The 3D surface plots and associated contour mappings indicate that this THz amplitude is definitely profile dependent. In fact, one expects the q-Gaussian and the low-b sech-Gaussian pulses to produce the most efficient THz generation. This quality is because they possess a sharp intensity profile. The sharply localized intensity pattern should lead to a stronger gradient in the radial direction. The response is a greater modulation on the nonlinear current. In contrast, high-order super-Gaussian pulses are much less efficient. This is due to their flat-top spatial profile and weaker ponderomotive gradients. Every profile exhibits a maximum THz emission when ω/ω p ≈ 1.05 with the plasma response approaching resonance. The comparative study shows that it is the spatial beam localization that dominates THz yield and not the beam width. The findings of this work can help in developing a unified understanding of the profile-dependent THz generation mechanisms. Furthermore, the findings can help in the design of high efficiency beam-shaped laser-plasma THz sources.