Terahertz radiation generated by shell electrons in the bubble regime via the interaction between an intense laser and underdense plasma

TL;DR

This paper demonstrates a novel method for generating backward terahertz radiation via electron refluxing along the bubble shell in laser-plasma interactions, with potential applications in plasma diagnostics.

Contribution

It introduces a new scheme for terahertz generation involving shell electrons in the bubble regime, supported by simulations and theoretical models.

Findings

Terahertz radiation is produced by refluxing shell electrons.

Bubble shape influences the radiation frequency.

The scheme works in various plasma density profiles.

Abstract

Backward terahertz radiation can be produced by a high-intensity laser normally incident upon an underdense plasma. It is found that terahertz radiation is generated by electrons refluxing along the bubble shell. These shell electrons have similar dynamic trajectories and emit backward radiations to vacuum. This scheme has been proved through electron dynamic calculations as well as by using an ionic sphere model. In addition, the bubble shape is found to influence the radiation frequency, and this scheme can be implemented in both uniform and up-ramp density gradient plasma targets. The terahertz radiation may be used for diagnosing the electron bubble shape in the interaction between an intense laser and plasma. All results are presented via 2.5 dimensional particle-in-cell simulations.