A Q-switched laser is a laser to which the technique of active or passive Q switching is applied, so that it emits energetic pulses. Typical applications of Q-switched lasers are material processing, pumping nonlinear frequency conversion devices, range finding, and remote sensing.

Q switching is a technique to obtain energetic short pulses from a laser. Here, the cavity losses are kept on a high level until the pumped gain medium has stored a significant amount of energy. Then, the losses are suddenly reduced to a small value, so that the power of the laser radiation in the cavity builds up very quickly. This results in a short pulse, the energy of which can be in the millijoule range even for rather small lasers. Lasers to which such a technique is applied are called Q-switched lasers.