Passive and active Q switch

Passive and active Q switch

Q switching technology

The Q-switching method is an efficient approach to acquiring brief pulses of high power. Q value is an index to review the quality of an optical resonator in a laser (the “quality factor”). Q-switching technology, additionally referred to as Q-switching innovation, is a technology that compresses the constant laser result right into a very slim pulse, therefore increasing the peak power of the light source by numerous orders of size.

In the process of the Q, gain tool prior to shop enough energy, maintaining high cavity loss, the laser resonator laser at this time because of the limit is expensive, do not create laser shock, makes the top degree population can be a multitude of accumulation, when gathered to saturation worth, the loss of the cavity rapidly lowered to an extremely tiny value, As a result, in a short time, a lot of the power saved in the top degree fragments is exchanged laser power, and a strong laser pulse outcome is produced at the outcome end.

Q switching technology is generally split into energetic Q switching technology (acousto-optic Q switching as well as electro-optic Q switching) and easy Q switching technology.

Passive Q switch

In passive Q-switching technology, a saturable absorber (typically a strong saturable absorber, such as Gr: YAG) is embeded in the resonator of a laser, and its saturation absorption effect is used to periodically regulate the loss of the resonator to obtain the pulsed light output. At the start, the autofluorescence in the cavity is really weak, the absorption coefficient of the saturable absorber is large, the light passage is very low, and also the cavity remains in a state of high loss, so the laser oscillation can not be formed.

Continue working with the light pump, the inversion of bit number to accumulate, lumen fluorescence stamina tirelessly, when the light intensity reaches a specific value, the saturable absorber absorption saturation value abruptly “blanch,” and the result was a laser pulse. After the light area inside the cavity is abated, the saturable absorber recovers absorption features, and the process is repeated to obtain the pulse light output.

Typically utilized passive Q-switched crystals are: Co:spinel crystal, Cr:YAG, Cr:GSGG, V:YAG, Cr:YSO, etc

Active Q switch

1) Acousto-optic Q switch

Acousto-optic Q switching technology 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 extremely high (low loss), which makes it very easy to produce laser oscillation. When there is an ultrasonic wave, the thickness of the acoustic and optical tools is adjusted regularly, resulting in the routine modification of the refractive index as well as the deflection of the beam of light.

Right now, the Q value of the resonator is extremely reduced (high loss), and the number of particles in the upper level is gathering rapidly. Therefore, we can manage the loss in the tooth cavity by regulating the ultrasonic wave, and after that obtain the pulse light output.

Typical acousto-optic Q crystals are: TeO2 and so forth.

2) Electro-optic Q switch

Electro-optic Q switching is to utilize the electro-optic effect of the crystal to include an action voltage on the crystal to change the reflection loss of photons in the cavity. A high voltage is applied to the crystal, at this time, the electro-optic Q switch remains in the off state, the resonator remains in the low Q state, and the system is in the power storage space state. When the number of inverted particles in the resonator gets to the optimum, the high pressure on the crystal is unexpectedly gotten rid of, and also the resonator is in a high Q state, developing a pulsed laser outcome.

Typically utilized electro-optic Q crystals are: BBO, LiNbO3, LiTaO3( LT), KTP, etc.

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