Q-switching
The Q-switching method is an efficient method to get short pulses with high energy. Q worth is an index to review the quality of optical resonator in laser– “quality element”. Q-switching modern technology, also known as Q-switching modern technology, is a modern technology that compresses the constant laser outcome right into a very narrow pulse, hence raising the peak power of the light by a number of orders of magnitude.
In the process of the Q, gain tool prior to shop sufficient energy, keeping high cavity loss, the laser resonator laser at this time due to the threshold is too expensive, do not create laser shock, makes the upper-level population can be a great deal of buildup when built up to saturation value, the loss of the cavity swiftly reduced to a really tiny value, Consequently, quickly, most of the energy saved in the upper degree fragments is converted into laser power, and a solid laser pulse outcome is created at the result end.
Q-switching technology is mainly divided into active Q-switching technology (acousto-optic Q-switching and also electro-optic Q-switching) and also easy Q-switching technology.
Passive Q-switching
In passive Q-switching technology, a saturable absorber (generally a solid saturable absorber, such as Gr: YAG) is set in the resonator of a laser, and also its saturation absorption impact is used to regularly control the loss of the resonator to acquire the pulsed light output. In the beginning, the autofluorescence in the cavity is really weak, the absorption coefficient of the saturable absorber is very large, the light passage is very reduced, and also the cavity remains in a state of high loss, so the laser oscillation can not be developed. Continue operating with the light pump, the inversion of bit number accumulates, and lumen fluorescence toughness tirelessly, when the light strength reaches a particular worth, the saturable absorber absorption saturation worth suddenly “blanch” and also the output laser pulse, and then light field inside the cavity is abate, saturable absorber recover absorption qualities, and after that repeat the process to obtain the pulse light outcome.
Frequently utilized passive Q-switched crystals are: cobalt spinel, Cr: YAG, Cr: GSGG, V: YAG, Cr: YSO, etc
Active Q-switching
(1) Acousto-optic Q-switching
Acousto-optic Q switching innovation refers to the acousto-optic medium in the resonator. When there is no ultrasonic wave, the beam can freely travel through the acousto-optic medium. The Q value of the cavity is really high (reduced loss), which is simple to create laser oscillation. When there is an ultrasonic wave, the density of acoustic as well as optical tools adjusts periodically, leading to the routine adjustment of the refractive index as well as the deflection of the beam. At this time, the Q worth of the resonator is very low (high loss), and also the variety of fragments in the upper degree collects quickly. For that reason, we can manage the loss in the cavity by controlling the ultrasonic wave, and after that obtain the pulse light result.
Typical acousto-optic Q crystals are: TeO2 and so forth
(2) Electro-optic Q-switching
Electro-optic Q-switching is to utilize the electro-optic effect of the crystal to add a step voltage on the crystal to change the representation loss of photons in the cavity. A high voltage is applied to the crystal, at this time, the electro-optic Q switch is in the off state, the resonator remains in the low Q state, and also the system is in the energy storage state. When the number of upside-down bits in the resonator reaches the maximum, the high pressure on the crystal is unexpectedly removed, as well as the resonator remains in a high Q state, developing a pulsed laser result.
Typically utilized electro-optic Q crystals are: BBO, LiNbO3, LiTaO3(LT), KTP, and so on