Modeling of intense terahertz wave generation with controlled field distribution

Abstract

We report the results of a theoretical model and numerical investigations for an efficient intensity distribution-tunable terahertz (THz) radiation generation by two color Hermite cosh Gaussian lasers pumped in periodic density gas plasma. The effect of various laser parameters like b (decentered parameter of the cosh function), s (mode index of the Hermite function), δ (initial phase difference between two lasers), and νen (electron neutral collision frequency) on the THz field distribution, amplitude, and efficiency is investigated. The largest peak of the THz field is obtained for s=1, b=0, δ=0, π, 2π, and ω≈ωp (resonant excitation) at x=0 (forward emission in the direction of the laser propagation axis). It is found that THz radiation is highly intense for s=1, b=0, νen=0, and ω≈ωp compared to any other set of laser and plasma parameters. This study also reveals that the THz peak field and efficiency decrease monotonically with electron collision frequency. The THz field of ∼G V m−1 with an efficiency of ∼3% for the optimum laser and plasma parameters can be obtained in this scheme.