sentences:  This readies them for amplification via stimulated emission when a small amount of laser light, generated externally in a fibre optic, is fed into the beamlines.The glass is not particularly effective at transferring power into the beam, so to get as much power as possible back out, the beam is reflected through the glass four times in a mirrored cavity, each time gaining more power.When this process is complete, a Pockels cell "switches" the light out of the cavity.