Editing Q-switching (section)

===Variants===
[[image:Regenerative Amplifier.png|thumb|right|Regenerative amplifier. Red line: Laser beam. Red box: Gain medium. Top: [[acousto-optic modulator|AOM]]-based design. Bottom: The Pockel's cell-based design needs thin film polarizers.
The direction of the emitted pulse depends on the timing.]]

[[Jitter]] can be reduced by not reducing the Q by as much, so that a small amount of light can still circulate in the cavity. This provides a "seed" of light that can aid in the buildup of the next Q-switched pulse.

With [[Cavity dumper|cavity dumping]], the cavity end mirrors are 100% reflective, so that no output beam is produced when the Q is high. Instead, the Q-switch is used to "dump" the beam out of the cavity after a time delay. The cavity Q goes from low to high to start the laser buildup, and then goes from high to low to "dump" the beam from the cavity all at once. This produces a shorter output pulse than regular Q-switching. Electro-optic modulators are normally used for this, since they can easily be made to function as a near-perfect beam "switch" to couple the beam out of the cavity. The modulator that dumps the beam may be the same modulator that Q-switches the cavity, or a second (possibly identical) modulator. A dumped cavity is more complicated to align than simple Q-switching, and may need a [[Control system|control loop]] to choose the best time at which to dump the beam from the cavity.

In regenerative amplification, an [[optical amplifier]] is placed inside a Q-switched cavity. Pulses of light from another laser (the "master oscillator") are injected into the cavity by lowering the Q to allow the pulse to enter and then increasing the Q to confine the pulse to the cavity where it can be amplified by repeated passes through the gain medium. The pulse is then allowed to leave the cavity via another Q switch.