PERFORMANCE OF LARGE-APERTURE OPTICAL SWITCHES FOR HIGH-ENERGY INERTIAL-CONFINEMENT FUSION LASERS

We describe the design and performance of large-aperture (> 30 cm x 30 cm) optical switches that have demonstrated, for the first time to ou r knowledge, active switching of a high-energy ( > 5 kJ) optical pulse in an inertial-confinement fusion laser. These optical switches, whic h consist of a plasma-electrode Pockels cell (PEPC) and a passive pola rizer, permit the design of efficient, multipass laser amplifiers. In a PEPC, plasma discharges on the faces of a thin (1-cm) electro-optic crystal (KDP or KDP) act as highly conductive and transparent electro des. These plasma electrodes facilitate rapid ( < 100 ns) and uniform charging of the crystal to the half-wave voltage and discharging back to 0 V. We discuss the operating principles, design, optical performan ce, and technical issues of a 32 cm x 32 cm prototype PEPC with both K DP and KDP crystals, and a 37 cm x 37 cm PEPC with a KDP crystal for the Beamlet laser. This PEPC recently switched a 6-kJ, 3-ns pulse in a four-pass cavity.