Towards realizing optical injection of electrons in resonantly excited plasma wakefields

The concept of optical injection of plasma background electrons into resonantly driven laser wakefields has been extensively studied theoretically [D. Umstadter et al., Phys. Rev. Lett. 76, 2073 (1996)]. It was shown that when a strong 1-D wakefield is ponderomotively excited by an ultra-short laser pulse comparable in duration to the plasma wave and a similar transverse laser pulse, but otherwise tightly focused onto the wakefield, is introduced, a relativistic electron bunch with a very narrow (a few %) energy distribution, and very short duration (10´s fs) is produced. This concept is actively being investigated experimentally using the University of Michigan´s Hercules laser system. We report our progress toward experimentally realizing this concept.