Terahertz Radiation Generation From Beat Laser Interaction With Step Density Rippled Plasma

Abstract

The nondestructive nature of plasma has garnered significant interest in generating high-peak-power terahertz (THz) pulses through the interaction of ultrafast lasers with plasma. Here, this article presents an analytic formalism for the generation of high-field THz radiation through the beating of frequency-varying lasers in the rippled surface density hot collision-free plasma. Laser propagating oblique at an angle $\theta $ to plasma imparts an oscillatory velocity to plasma electrons that generates a nonlinear ponderomotive force at beating frequency having frequency difference $\omega _{1}-\omega _{2}=\omega $ that lies in the THz. Interaction time of laser and plasma extends with the application of frequency-varying laser, while density ripple plays crucial role in phase matching. Frequency-varying laser and density ripple jointly enhance the field strength, while field enhancement occurs further due to the Langmuir wave coupling when beat frequency approaches plasma frequency. Optimization of various scaling laws, such as laser angle with plasma, time-dependent frequency of laser, density ripple, and laser intensity, achieves the desired power and radiation that lie in THz range, suitable for various ambitious applications.