Abstract
Laser wakefi eld acceleration, based on the effect of plasma waves excitation in the wake of an intense
laser pulse, is now regarded as a basis for the next generation of charged particle accelerators. In order
to generate a bunch with high quality and stability, required for applications, the electrons should be duly
injected into the wakefi eld and this injection should be controllable. This paper reviews optical injection
of electrons into the wakefi eld for a stable and a controllable electron beam generation. The wakefi eld is
generated by a laser pulse. The second laser pulse collides with the fi rst pulse at 180 and at 135 degrees
realizing optical injection of an electron bunch. The electron bunch has high stability and high
reproducibility compared with single pulse electron generation.
