lasers which emit optical pulses, relying on the method of Q switching. Q-switching , also known as giant pulse formation, is a technique by which a laser can be made to produce a pulsed output beam. 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 such lasers are material processing (e.g. cutting, drilling, laser marking ), pumping nonlinear frequency conversion devices, range finding , and remote sensing. That's because Q-Switched lasers provide high energy, high peak power pulses at high repetition rates. As Q - switching combines both short and long pulses. So it can also be used as medical area. For example, laser surgery such as tattoo removal, pigmented lesions and hair removal applications.
Now we have Q-switched diode-pumped green lasers, it's using rapid, high pulsed Q- Switched technology. More than a decade ago, Q-Switched Alexandrite laser was introduced operating at a wavelength of 755nm. These lasers have become highly proficient tools for the skin care professionals and dermatologist. In recent years, Q-switched lasers are also used at measurement purposes by measuring the time it takes for the pulse to get to some target and the reflected light arriving.
The operation of a normal Q-switched laser is like this. In the resonator, blocking one of the mirrors with a modulator ( the Q-switch ). The energy gets no way to go but build up and cumulate until the modulator switched on. Then a few spontaneous photons quickly stimulate the laser to emit all the stored energy in a giant, Q-switched pulse. The duration of pulse is depends on resonator's length, output coupling , the repetition rate and the pump power, etc.
Note that the high pulse energies and peak powers can raise serious laser safety issues even for lasers with low average output power. A single shot into an eye will in many cases be the last thing that an eye has seen. Such risks can be substantially reduced by using Q-switched lasers operating at eye-safe wavelengths .