Stimulated emission from a laser-wiggled electron beam travelling in an electrostatic wave

Abstract

An axial emission process by a relativistic electron beam travelling in a laser beam and an electrostatic wave propagating in the direction antiparallel to the electron-beam direction (‘electric wiggler’), which is different from free-electron two-quantum Stark (FETQS) emission, is identified, and the laser gain through this process is investigated using relativistic quantum kinetics. The transverse a.c. source current for this axial emission is produced by the laser field acting as a classical electromagnetic wave to wiggle the electron in the transverse direction. From the viewpoint of quantum kinematics, this radiation-wiggled one-quantum induced Stark (RWOQIS) emission is exactly the same as FETQS emission in which the equivalent transverse source current needed for the axial emission is due to the intrinsic electron spin angular momentum. However, these two emissions differ in dynamics, since the former is an one-quantum process while the latter is a two-quantum process. It is found that the laser gain by RWOQIS emission increases with the laser intensity when ¦eA0/mc2¦ ≪ 1 and decreases with the inverse of the square of the laser intensity when ¦eA0/mc2¦ ≫ 1, where A0 is the potential amplitude of the laser wave and mc2 is the electron rest energy. This newly found emission is an inherently stimulated one, and does not have a corresponding spontaneous emission.