BROAD-BAND POCKELS CELL AND DRIVER FOR A MARK III-TYPE FREE-ELECTRON LASER

A Pockels cell with an operating range of 2 to 10 mum has been designe d, constructed, and tested for use with the Vanderbilt free electron l aser. The Pockels cell can be continuously adjusted to switch out from 80 ns to the full 6 mus duration of the FEL macropulse. The extinctio n ratio is better than 180:1 and the optical pulse is square with rise and fall times under 10 ns. The high voltage drivers are based on sem iconductor switches that are compact and mounted directly to the Pocke ls cell; this design avoids problems associated with fast, high voltag e pulses traveling in cables. In addition, designs for two alternative drivers to generate optical pulses with durations ranging from a few nanoseconds down to the subnanosecond regime are presented here. Proto types using single high voltage transitions have been constructed and tested electrically.