The technique allows the production of light pulses with extremely high (gigawatt) peak power, much higher than would be produced by the same laser if it were operating in a continuous wave (constant output) mode.

Hellwarth and F.J. McClung at Hughes Research Laboratories using electrically switched Kerr cell shutters in a ruby laser.

Due to losses from spontaneous emission and other processes, after a certain time the stored energy will reach some maximum level; the medium is said to be gain saturated.

At this point, the Q-switch device is quickly changed from low to high Q, allowing feedback and the process of optical amplification by stimulated emission to begin.

In this case, the Q-switch is a saturable absorber, a material whose transmission increases when the intensity of light exceeds some threshold.

Initially, the loss of the absorber is high, but still low enough to permit some lasing once a large amount of energy is stored in the gain medium.

Ideally, this brings the absorber into a state with low losses to allow efficient extraction of the stored energy by the laser pulse.

The pulse repetition rate can only indirectly be controlled, e.g. by varying the laser's pump power and the amount of saturable absorber in the cavity.

Large-scale laser systems can produce Q-switched pulses with energies of many joules and peak powers in the gigawatt region.

[8] Q-switched lasers are also used to remove tattoos by shattering ink pigments into particles that are cleared by the body's lymphatic system.

In 2013 a picosecond laser was introduced based on clinical research which appears to show better clearance with difficult-to-remove colours such as green and light blue.

[citation needed] Q-switched lasers can also be used to remove dark spots and fix other skin pigmentation issues.