Efficient terahertz (THz) generation by nonlinear mixing of bicolor top-hat lasers in hot plasma

• Published in: Physics of plasmas 2020-02, Vol.27 (2)
• Main Authors: Manendra, Singh, Kunwar Pal, Bhati, Ruchi, Malik, Anil K
• Format: Article
• Language: English
• Subjects: Amplitudes; Electron energy; Lasers; Modulation; Phase matching; Plasma; Plasma density; Plasma frequencies; Plasma physics; Wavelengths
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.5121913

We report a theoretical model of radially polarized terahertz (THz) wave emission by nonlinear mixing of bicolor, radially polarized lasers having a top-hat envelope profile [ s   ( profile   index ) ≥ 1] in density modulated hot plasma. We investigate the effect of the laser profile index on the emitted THz field profile and found that THz field amplitude and peak location changes with the laser profile index. Our numerical investigations show that THz field amplitude is the highest around ω p ≈ ω 1 − ω 2 (where ω p is the plasma frequency and ω 1   and     ω 2 are the laser frequencies). We observe that phase matching can be achieved with the help of the plasma density modulation wave number. The plasma density modulation wave number increases with electron temperature and decreases with the frequency mismatch between ω p and ω 1 − ω 2. We found that the conversion efficiency is maximum at ω 1 − ω 2 ≈ ω p and increases fivefold with an increase in electron thermal velocity ( v th) from v th = 0 to v th = 0.2 c, where c is the speed of light.