1. Q-switch modern technology
Q-switch technique is an effective method to get short pulses with high energy. Q value is an index to evaluate the quality of optical resonator in laser– “quality element”. Q-switching modern technology, also called Q-switching innovation, is a modern technology that presses the continual laser output into a very slim pulse, therefore raising the peak power of the light source by a number of orders of magnitude.
In the process of the Q, gain medium prior to shop sufficient energy, preserving high cavity loss, the laser resonator laser at this time due to the limit is too expensive, do not produce laser shock, makes the upper level populace can be a lot of build-up, when collected to saturation worth, the loss of the cavity promptly minimized to an extremely little worth, For that reason, quickly, the majority of the energy kept in the upper level fragments is exchanged laser energy, as well as a solid laser pulse result is generated at the outcome end.
Q-switch innovation is generally separated right into energetic Q switching innovation (acousto-optic Q switching and also electro-optic Q switching) and passive Q switching technology.
2. Passive Q-switch
In passive Q-switch innovation, a saturable absorber (normally a solid saturable absorber, such as Gr: YAG) is set in the resonator of a laser, and also its saturation absorption impact is utilized to regularly control the loss of the resonator to obtain the pulsed light outcome.
At the start, the autofluorescence in the cavity is extremely weak, the absorption coefficient of the saturable absorber is very large, the light transmittance is very low, and the cavity remains in a state of high loss, so the laser oscillation can not be created. Remain to operate with light pump, the inversion of particle number to gather, lumen fluorescence stamina tirelessly, when the light intensity reaches a specific value, the saturable absorber absorption saturation value was all of a sudden “blanch” and also the result laser pulse, and after that light area inside the cavity is abate, saturable absorber recover absorption attributes, and afterwards repeat the procedure to obtain the pulse light output.
Frequently used passive Q-switched crystals are: co: spinel, Cr: YAG, Cr: GSGG, V: YAG, Cr: YSO, etc.
3. Active Q-switch
(1) Acousto-optic Q-switch
Acousto-optic Q-switching modern technology describes the acousto-optic tool in the resonator. When there is no ultrasonic wave, the beam of light can easily pass through the acousto-optic medium.
The Q value of the cavity is very high (reduced loss), which is very easy to produce laser oscillation. When there is ultrasonic wave, the density of acoustic as well as optical medium changes occasionally, leading to the regular adjustment of refractive index and also the deflection of the light beam. At this time, the Q worth of the resonator is very low (high loss), as well as the variety of fragments in the top level builds up swiftly. For that reason, we can manage the loss in the dental caries by regulating the ultrasonic wave, and then obtain the pulse light result.
Typical acousto-optic Q crystals are: TeO2 and so on.
(2) Electro-optic Q-switch
Electro-optic Q switching is to use the electro-optic effect of the crystal to include an action voltage on the crystal to readjust the reflection loss of photons in the cavity. A high voltage is applied to the crystal, right now, the electro-optic Q switch remains in the off state, the resonator is in the low Q state, and also the system remains in the energy storage space state. When the number of inverted particles in the resonator reaches the maximum, the high pressure on the crystal is instantly eliminated, and also the resonator remains in a high Q state, developing a pulsed laser outcome.
Commonly made use of electro-optic Q crystals are: BBO, LiNbO3, LiTaO3( LT), KTP, etc.
