Qswitched

Q-switched refers to lasers that emit short, high-peak-power optical pulses by rapidly changing the cavity’s quality factor, or Q. In a Q-switched laser, energy is stored in the gain medium with low losses, then released in a brief, intense burst when the losses are suddenly increased or the stored energy is otherwise unleashed. The result is a pulse with much higher peak power than the laser would produce in a continuous or long-pulse regime.

Q-switching methods are broadly categorized as active and passive. Active Q-switching uses external modulators such as electro-optic (Pockels) or acousto-optic devices controlled by electronics to interrupt and restore cavity feedback. Passive Q-switching employs saturable absorbers, either crystalline materials or semiconductor-based devices, that become transparent at high intensities. The choice of method affects pulse duration, energy stability, and complexity.

Typical pulse durations range from about 1 to tens of nanoseconds, with repetition rates from a few hertz to many tens of kilohertz. Pulse energy can span microjoules to millijoules, yielding peak powers that can reach megawatts in compact solid-state systems. The performance depends on the gain medium, cavity design, and Q-switching mechanism.

Common gain media include Nd:YAG and other solid-state lasers, often operated at 1064 nm with frequency-doubled output at 532 nm. Q-switching is also implemented in diode-poped fiber lasers and other materials.

Applications cover laser ranging and LIDAR, micromachining and materials processing, tattoo and pigment removal, dermatology, ophthalmology, and basic scientific research requiring precise, high-peak-power pulses.