Q-switches are devices used in the optical resonator of a laser to prevent lasing action until a high level of inversion is achieved in the lasing medium. There are many types of Q-switches. Examples include laser Q-switches, AO Q-switches, and micro Q-switches. Acoustic-optic Q-switches and AO Q-switches are optical devices consisting of an A/R coated fused silica cell which has an integral acoustic transducer. Micro Q-switches are used for ultra-short cavities. Q-switching is a technique by which a laser can be made to produce a pulsed output beam. This technique allows the production of light pulses with an extremely high peak power, much higher than would be produced by the same laser if it were operating in a continuous wave mode. Q-switching by laser Q-switches generates short pulse laser beams with high peak power that are desirable in most laser applications. Other Q-switches are commonly available.
Q-switches are designed for minimum insertion loss and to be able to withstand very high laser powers. In normal use an RF signal is applied to diffract a portion of the laser cavity flux out of the cavity. This increases the cavity losses and prevents oscillation. When the RF signal is switched off, the cavity losses decrease rapidly and an intense laser pulse evolves. A Q-switched laser includes a pump cavity, a laser medium in the pump cavity for generating laser light, and active and passive Q-switching elements for controlling Q-switching oscillation of laser light. A large quantity of heat is dissipated in Q-switches. Air-cooled Q-switches and water-cooled Q-switches are made to engage the problem of heat dissipation. While air-cooled Q-switches are for low grain cavities, water-cooled Q-switches are for high grain cavities. A Q-switch crystal provides high power laser pulses. Some commonly used Q-switch crystals are Co2+:MgAl2O4, Cr4+:YAG, and V3:YAG. Q-switches for Nd: Yag laser systems produce output power of 20 megawatts and pulse duration of less than 10 nanoseconds. Q-switch operation is generally carried out from 5 kHz to 50 kHz. Q-switches are specified according to their type, material used, carrier frequency, aperture, mode of cooling, and optical length. Q-switches are designed and manufactured to meet most industry specifications.
Q-switches are used in many applications. Examples include laser micromachining such as cutting, drilling, marking and engraving, medical science, and the defense industry such as range measurement and remote sensing. Q-switches should adhere to RS 232/45 standard.