Achieving subnanosecond optical switching using a Pockels cell requires an electrically optimized cell design and a compatible fast driver. We report on the design and operation of a high voltage, high speed switching circuit which is capable of achieving an optical switching time of 238 ps when used in conjunction with a 6 mm aperture Pockels cell. The driver uses a Marx-configured avalanche-transistor design to deliver up to 4 kV pulses into a 50 O load with approximately 12 ps jitter and an output pulse length of 7 ns. The Pockels cell is a commercially available unit. The observed optical switching time and the jitter in timing of the output pulse are the best currently reported in the literature. We also demonstrate the production of rectangular optical pulses of approximately 3.6 ns duration by reflecting the electrical pulse using a mismatched termination. © 2006 American Institute of Physics.