Effects of a prepulse in the femtosecond-pulse-driven Xe IX laser

We describe experiments that demonstrate the detrimental effect of a prepulse on the femtosecond-pulse-driven Xe ix laser. The mechanism of this effect is discussed in terms of the results of a hydrodynamic model of the preplasma formed by the prepulse. The benefit of inserting a simple electro-optic switch that allows full transmission of the main driving pulse, but reduces the prepulse to a level at which no preplasma is formed, is demonstrated experimentally.