Prepulse suppression for high-energy ultrashort pulses using self-induced plasma shuttering from a fluid target

The technique of self-induced plasma shuttering can be used to suppress prepulse energy from an ultrashort pulse. If a femtosecond pulse is incident upon a transparent target, the leading edge passes through while the peak reflects owing to ionization breakdown at the surface. We describe a fluid jet, enclosed in a vacuum chamber, that allows this technique to be used at high repetition rates. The jet has excellent stability and a fast (~500 micros) recovery time. At normal incidence, we demonstrate a reflection efficiency of 70% with a prepulse-to-main-pulse energy suppression ratio of >10, while at Brewster incidence we measure a reflection efficiency of 38% with a suppression ratio of nearly 400.