▶ Previous Artlcle : #2-1. Basics of LASER 

 

Coherence

 

Coherence means that when an atom receives energy from an external source, electrons in the atom change to an excited state and then turn to a resting state, and during this time, photons are emitted (spontaneous emission). However, the discharged photons move in all directions and are not coherent. There are some photons that move along the axial direction of the laser medium, and these move back and forth along the axial direction between the two reflective mirrors inside the resonator. And when these are absorbed by electrons in an excited state, the excited electrons turn to resting state and two photons with the same wavelength and phase are discharged. When this stimulated emission process is continuously repeated, the number of photons in the resonator increases geometrically. A population inversion occurs with most of electrons at an excited state and light becomes amplified. Photons amplified in this way have the same phase direction, and this is laser coherence.

 

 

<Coherence>

 

There are several advantages of using a collimated hand piece during laser toning. First, because the energy is not concentrated in one place and reacts with the tissue in an evenly distributed form, it allows delivery of the intended energy (fluence) more accurately than the focusing hand piece. Second, it reduces pain and recovery time because energy is not focused on one place. Third, it may reduce the risks of complications, such as petechia, hyperpigmentation, and hypopigmentation, that can occur after laser treatment using a focus handpiece.

 

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High Intensity

 

High intensity means that when an electron receives an external stimulus, it moves into an excited state and when it comes back to the resting state, it creates a new photon. The photon is then absorbed by another electron and this produces two photons. Such photons increase in number and are amplified by moving repeatedly between the two reflective mirrors in the resonator. Finally, a lump of photons with a powerful energy is produced and turned into a light that carries enough energy to interact with tissues. This is why lasers have higher energy compared to normal light. 

 

- To be continued