Plasma Pockels cell based optical switch for the National Ignition Facility

The National Ignition Facility (NIF), now under construction at Lawrence Livermore National Laboratory, is based on a multi-pass power amplifier. A key component in this laser design is an optical switch that closes to trap the optical pulse in the cavity for four gain passes and then opens to divert the optical pulse out of the amplifier cavity. The switch is comprised of a Pockels cell and a polarizer and is unique because it handles a beam that is 40 cm x 40 cm square and allows close beam packing in the 4 x 12 clusters for a total of 192 beams. Conventional Pockels cells do not scale to such large apertures or the square shape required for closing packing. The switch is based on a Plasma-Electrode Pockels Cell (PEPC). Recently, the authors demonstrated full operation of a prototype 2 x 1 PEPC. In this PEPC, the plasma spans two KDP crystals. A major advance in the 2 x 1 PEPC over the Beamlet PEPEC is the use of anodized aluminum construction which provides sufficient insulation to allow formation of the planar plasmas. In this paper, they present many interesting design details and experimental results which include observation of plasma and discharge effects which can degrade plasma uniformity including MHD plasma displacement from external return currents, current channel formation, and the effect of housing bias potential