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.