Generation of twisted terahertz radiation through plasma in the presence of a static electric field

The generation of twisted terahertz radiation through plasma is surveyed by employing a static electric field. By propagating two coaxial Laguerre–Gaussian lasers in plasma, the electron density distribution is perturbed. The static electric field imposes a velocity on the perturbed electron density. This current density can emit radiation at the terahertz frequency. We consider a plasma density distribution to produce terahetrz radiation with a Laguerre–Gaussian envelope. Three possibilities can be predicted for the orbital angular momentum of the twisted terahertz, which is expressed by a new selection rule. By choosing a suitable plasma distribution, only one of the orbital angular momentums can be produced.