This configuration is often called a Q-switch or gain switch and is used in many pulsed lasers. If an absorptive-reflective polarizer oriented at an angle to the beam is used, the laser beam either passes through or reflects from the polarizer depending on whether or not voltage is applied to the Pockels cell. This is the configuration used on NIF and in other regenerative, multi-pass laser amplifiers. The polarization at this point is horizontal which is the proper polarization to pass through the amplifier. About 10 nanoseconds after the pulse passes through the PEPC, we start to apply voltage to the PEPC in the form of a 17,000 volt pulse.
Light travels about one foot every nanosecond.
In the mean time, the optical pulse has passed through the cavity amplifier, reflected from the mirror at the far end of the cavity and passed through the amplifier a second time. This figure shows how the PEPC and a polarizer control the multi-pass operation of the NIF amplifier. The pulse then returns to the amplifier end of the cavity for two more gain passes. In the mean time, the PEPC voltage pulse ends and the voltage across the crystal decays to zero.