The difference between active and passive q-switching

Q-switching technology

Q switching technique is an effective method to acquire short pulses with high energy. Q worth is an index to review the quality of optical resonator in laser-- "quality variable". Q-switching innovation, also referred to as Q-switching technology, is an innovation that compresses the continual laser output right into a very slim pulse, hence enhancing the peak power of the light by several orders of size.

In the process of the Q, gain tool prior to storing sufficient energy, maintaining high cavity loss, the laser resonator laser at this time because of the threshold is expensive, do not produce laser shock, makes the top level population can be a large number of accumulation, when gathered to saturation value, the loss of the cavity quickly minimized to a really small worth, For that reason, in a short time, the majority of the power stored in the upper level fragments is converted into laser power, and a solid laser pulse output is created at the output end.

Q switching innovation is mainly separated right into active Q switching innovation (acousto-optic Q switching as well as electro-optic Q switching) and also easy Q switching modern technology.

The 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 its saturation absorption effect is used to periodically control the loss of the resonator to get the pulsed light result. At the start, the autofluorescence in the cavity is really weak, the absorption coefficient of the saturable absorber is large, the light transmittance is really reduced, as well as the cavity is in a state of high loss, so the laser oscillation can not be developed. Remain to operate with light pump, the inversion of particle number to collect, lumen fluorescence strength tirelessly, when the light strength reaches a certain value, the saturable absorber absorption saturation value was unexpectedly "blanch" and the output laser pulse, and after that light field inside the cavity is abate, saturable absorber restore absorption features, and then duplicate the process to get the pulse light result.

Generally made use of passive Q-switched crystals are: cobalt spinel, Cr: YAG, Cr: GSGG, V: YAG, Cr: YSO, etc.

Active Q-switching

(1) Acousto-optic Q switch

Acousto-optic Q switching technology describes the acousto-optic medium in the resonator. When there is no ultrasonic wave, the beam can openly go through the acousto-optic tool. 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 as well as optical medium adjustments periodically, resulting in the routine adjustment of refractive index as well as the deflection of the light beam. Currently, the Q value of the resonator is extremely low (high loss), and also the variety of bits in the upper level collects rapidly. For that reason, we can manage the loss in the cavity by regulating the ultrasonic wave, and afterwards obtain the pulse light outcome.

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

(2) Electro-optic Q switching

Electro-optic Q switching is to make use of the electro-optic impact 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 related to the crystal, right now, the electro-optic Q button is in the off state, the resonator is in the reduced Q state, and the system remains in the energy storage space state. When the number of upside down particles in the resonator reaches the maximum, the high pressure on the crystal is instantly gotten rid of, and the resonator is in a high Q state, developing a pulsed laser output.

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

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