Simultaneous spectral calibration of two phase plates

The beam divergence angle is measured of the Q-switched laser pulse resulting from a resonator switched with a Pockels cell which is driven with a slowly opened circuit using a transformer. The rise time of the output voltage of this transformer type circuit is controllable. After optimization, the beam divergence of the present laser system is decreased by 30% compared with the conventional system using a Krytron. A model concerning the mode selection in the resonator is proposed.