• #9-1. Q-switched Nd:YAG Laser


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    Q-switching System


    Q-switched Nd:YAG(Neodymium-doped Yttrium Aluminum Garnet) Laser is a Non-ablative Laser, unlike the CO2 Laser, Er:YAG Laser which was explained last time. It is a solid-state laser using the Nd: YAG crystal as a medium, and produces the laser of 1064nm, 1320nm and 1440nm wavelengths in the infrared region.


    Nd:YAG Laser has the continuous wave and the pulsed output beam. One of the techniques for creating the pulsed output beam is the Q-switching method.


    Q-switching method produces high peak power of about giga watts, compared to continuous waves, thereby creating the selective photothermal, photomechanical, and photoacoustic effects in laser tissue interaction.



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    The overview of the Q-switching is as follows: Laser activity begins when a threshold condition is met. The optical amplification energy exceeds the loss energy such as diffraction, absorption, scattering, etc. when the reciprocating motion is made once in the resonator. This laser continues to be released until the stored energy is exhausted or the pump source stops. 


    If the laser activity can be prevented for a long time until the maximum energy is stored, and if this accumulated energy can be released in a very short time, higher pulse energy can be created for a very short time(nanosecond, picosecond). This method of generating a laser beam is called 'Q-switching'.


    Usually, a Q-switching system is created by inserting various types of attenuators, such as pockels cell, etc., in a resonator(Figure. 1).



    Figure 1. Q-switching system. 




    - To be continued

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