Distinction between passive and active Q-switch

Distinction between passive and active Q-switch

1. Q switch technology

Q switch method is an effective technique to obtain brief pulses with high energy. The Q value is an index to examine the quality of optical resonator in laser — “quality factor”. Q-switching technology, additionally called Q-switching technology, is an innovation that presses the constant laser outcome into a very slim pulse, therefore boosting the peak power of the source of light by several orders of size.

In the process of the Q, gain tool prior to shop enough energy, maintaining high cavity loss, the laser resonator laser currently as a result of the threshold is too high, do not generate laser shock, makes the upper degree population can be a great deal of accumulation, when built up to saturation worth, the loss of the cavity promptly decreased to a really tiny worth, Therefore, quickly, the majority of the energy stored in the upper level fragments is exchanged laser energy, and also a solid laser pulse output is created at the result end.

The Q switching innovation is primarily divided right into active Q switching technology (acousto-optic Q switching and also electro-optic Q switching) and easy Q switching modern technology.

2. Active

Acousto-optic Q switch

Acousto-optic Q switching innovation describes the acousto-optic medium 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 really high (low loss), which is very easy to create laser oscillation. When there is ultrasonic wave, the thickness of acoustic and also optical medium changes regularly, causing the routine adjustment of refractive index and the deflection of the light beam. At this time, the Q value of the resonator is really low (high loss), and the number of particles in the top level builds up rapidly. Consequently, we can control the loss in the dental caries by managing the ultrasonic wave, and then get the pulse light result.

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

Electro-optic Q switch

Electro-optic Q switching is to utilize the electro-optic effect of the crystal to add a step voltage on the crystal to adjust the reflection loss of photons in the cavity. A high voltage is applied to the crystal, currently, the electro-optic Q button remains in the off state, the resonator remains in the low Q state, and the system is in the energy storage state. When the number of inverted particles in the resonator reaches the maximum, the high pressure on the crystal is unexpectedly gotten rid of, and the resonator remains in a high Q state, developing a pulsed laser result. For example, the properties of electro-optic crystal BBO can be used to fabricate BBO Pockels cell.

Generally made use of electro-optic Q crystals are: BBO, LiNbO3, LiTaO3( LT), KTP, and so on.

3. Passive

In passive Q-switching innovation, a saturable absorber (generally a solid saturable absorber, such as Gr: YAG) is embeded in the resonator of a laser, and also its saturation absorption result is utilized to periodically manage the loss of the resonator to obtain the pulsed light outcome.

At the beginning, the autofluorescence in the cavity is really weak, the absorption coefficient of the saturable absorber is huge, the light passage is extremely reduced, as well as the cavity remains in a state of high loss, so the laser oscillation can not be created. Remain to work with light pump, the inversion of fragment number to collect, lumen fluorescence strength tirelessly, when the light intensity reaches a certain worth, the saturable absorber absorption saturation value was suddenly “blanch” and the result laser pulse, and afterwards light area inside the cavity is abate, saturable absorber bring back absorption features, and afterwards duplicate the process to get the pulse light result.

Commonly utilized passive Q-switched crystals are: cobalt spinel, Cr: YAG, Cr: GSGG, V: YAG, Cr: YSO, etc.

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