Average Power Switching Technology for High Energy and Repetition- Rate Laser Systems

High-energy and repetition-rate laser systems under development for studying of inertial fusion energy (IFE) and high energy intensity physics use a multi-pass amplifier architecture to reduce costs and physical size of the facility. In these amplifier systems, the combination of repetition-rate Pockels cell and a thin-film polarizer forms an optical switch, which is key to suppress selfoscillations or control the number of passes that laser-pulse train make through the amplifier cavity. In this case, Pockels cell should adapt for high average power application. However, the optical absorption, even weak in the case of a Pockels cell, can lead to thermal effects which degrade its performance. These include wave-front distortion, thermal stress, and stress-induced depolarization. The undesirable effects must be carefully controlled in a high performance laser system. In addition, the dimension of laser beam is typically designed as large as several centimeters to keep the influence below the damage threshhold of various optical components, thus the Pockels cell should also be able to scale to large aperture. The plasma-electrodes Pockels’ cell (PEPC), come up by LLNL in 1984, can adopt thin crystal, and be scaled to large aperture. However, the thermal load in the electro-optic crystal can’t be carried off efficiently because of the low pressure environment. From the said above, no existing switching technology could meet the needs of the next generation laser drivers. To overcome this difficulty, we propose and demonstrate for the first time, as far as we kown, a reflecting Pockels cell (RPC) that has thermal properties that make it advantageous for high energy and repetition-rate laser systems.