Performance of large-aperture optical switches for high-energy inertial-confinement fusion lasers

Abstract

We describe the design and performance of large-aperture (>30 cm × 30 cm) optical switches that have demonstrated, for the first time to our knowledge, active switching of a high-energy (>5 kJ) optical pulse in an inertial-confinement fusion laser. These optical switches, which consist of a plasma-electrode Pockels cell (PEPC) and a passive polarizer, 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 KD*P) act as highly conductive and transparent electrodes. 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 performance, and technical issues of a 32 cm × 32 cm prototype PEPC with both KDP and KD*P crystals, and a 37 cm × 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.

Growth and characterization of L‐alanine doped KDP crystals

“…The acousto-optic tunable filters have been developed using KDP [3]. For the inertial confinement fusion (ICF) experiments the performance of large aperture switches based on KDP have been assessed for high power laser experiments [4,5]. Rapid growths of large size (40-55 cm) KDP crystals [6] as well as rapid growth of KDP crystals with additives [7] have facilitated to obtain perfect KDP crystals for device application on large scale.…”

Advanced conceptual design report for the Z-Beamlet laser backlighter

“…This design takes advantage of several technological advances that were not available when Nova was built, and will allow for Z-backlighter performance exceeding that of a single Nova beam with greatly reduced complexity and cost. The development of a full-aperture plasma-electrode Pockels cell (PEPC) [2,3] allows the beam to traverse the main cavity amplifier four times to provide effective use of the gain, as well as efficient use of energy stored in the amplifiers. This feature allows the system to fit into a much smaller space than comparable Nova technology, and enables deployment within space available in Building 986 at Sandia.…”

The National Ignition Facility: Ushering in a new age for high energy density science

“…A key advance was the optical switch, called the "plasma electrode pockels cells ͑PEPCs͒," large planar electrodes that can have their polarization transmission direction switched by changing the voltage across them. 17 Electrical connections to the surfaces are achieved with a plasma on either side of each cell. Since the laser beams are polarized, the PEPCs are set so their initial polarization direction allows transmission.…”