A Q-switched laser (quality-switched laser) is a laser that emits short, high power pulses; Q-switching, also known as giant pulse formation, allows a laser to produce a pulsed beam of light. The technique produces light pulses with very high power -- much higher than would be produced by the same laser operating in a constant output (continuous wave) mode.
Compared to other techniques for pulse generation with lasers, Q-switching allows lower pulse repetition rates, higher pulse energies, and longer pulse durations. Thanks to these differences, Q-Switched lasers have become recognized largely as the gold standard for most laser tattoo removal because they more effectively break up the ink into particles which can then be eliminated by the patient’s own immune system.
Due to their use of selective photothermolysis, Q-switched and other pulsed lasers are also useful for laser hair removal and the removal/reduction of hyperpigmentation, as well as for vascular lesions such as cosmetically undesirable broken blood vessels, spider nevi, and hemangiomas.