Effect of self-injection on ultraintense laser wake-field acceleration

The self-injection of plasma electrons which have been accelerated to relativistic energies by a laser pulse moving with a group velocity less than the speed of light with $I{\lambda }^2>5\mathrm{}\times {10}^{19}\mathrm{W}\mu {\mathrm{m}}^2/{\mathrm{cm}}^2$ is found via particle-in-cell simulation to be efficient for laser wake-field acceleration. When the matching condition $a_0>~{(2\mathrm{}}^{1/4}\omega /{\omega }_{\mathrm{pl}}{)}^{2/3}$ is met, the self-injection, along with wave breaking, dominates monoenergetic electron acceleration yielding up to 100 MeV energies by a 100 TW, 20 fs laser pulse. In contrast to the injection due to wave-breaking processes, self-injection allows suppression of production of a Maxwell distribution of accelerated particles and the extraction of a beam-quality bunch of energetic electrons.