Laser Q-switching technology first appeared in 1962. It is an important breakthrough in the history of laser development. It is a special technology adopted to compress the laser output pulse width (nanosecond level) and increase the peak power of the pulse; the basis of this technology is one A special key component-fast intracavity optical switch, called laser Q-switch, or Q-switch for short. In short, a technology that achieves high peak power instantaneously.
After the high peak power light emitted by this laser is absorbed by the pigment, the pigment is crushed under the effect of heat, and the pigment cluster is rapidly expanded and broken. Then these small fragments are swallowed by the phagocytes in the body and cleared out of the body due to the time of releasing energy Very short, so that the heat generated by it will not be transmitted to the surrounding tissues and epidermis, and will not cause damage to the normal skin, so in principle, no scar will be formed after treatment. It completely changes the current status of the treatment of pigmented skin problems, and has achieved nearly perfect results for the treatment of pigmentation diseases. It can also repair and improve scars, wrinkles, enlarged pores, etc.
In recent years, picosecond lasers have been launched to shorten the pulse width to 10-12 s. Make the treatment of hyperpigmented skin diseases safer.
The working principle of laser Q-switching technology is to intentionally reduce the Q value of the resonant cavity without laser oscillation after the start of excitation, and the number of particles in the working substance will increase continuously, and then at a certain moment, the resonant cavity will suddenly and rapidly increase The Q value makes the laser oscillation rapidly occur in the cavity, and the high-speed accumulated inversion particle energy is quickly released in a short time, so as to obtain a laser output with a very narrow pulse width and high peak power.
The YAG crystal emits natural light under the light pump of the xenon lamp. It becomes linearly polarized light along the x direction. If no voltage is applied to the modulation crystal, the light passes through the crystal along the optical axis without changing its polarization state. After being reflected by the total reflection mirror, it passes through the modulation crystal and polarizing prism again (without change) , The electro-optic Q switch is in the “on” state. If a voltage is applied to the modulating crystal, due to the longitudinal electro-optic effect, when the linearly polarized light in the x direction passes through the crystal, it is reflected back by the total mirror and passes through the modulating crystal again. The polarization plane is relative to When the incident light is deflected by 900, the polarized light can no longer pass through the polarizing prism, and the Q switch is in the “off” state. If the xenon lamp dares to ignite, adjust the voltage on the crystal beforehand to make the resonant cavity in the “off” low-Q state, blocking Laser oscillation is formed. When the number of particles with energy level inversion on the laser reaches the maximum value, the voltage on the crystal is suddenly removed, so that the laser is instantly in a high-Q state, and a blood avalanche-like laser oscillation occurs, and a giant pulse can be output.
Note 1: Pigmented skin diseases include: freckles, pigmented nevus, coffee spots, chloasma, freckle-like nevi, Riehl melanosis, perioral sunspots, Ota nevus, pigmented hair epidermal nevus, general sunspot, facial －Neck hair follicular erythema melanosis, pityriasis rosea pigmentosa, nevus stains, congenital pigmented nevus, folds of reticular pigment abnormalities, Mongolian spots, tattoos, vitiligo, non-pigmented moles, eccentric acquired leukoplakia, hereditary Symmetric dyschromia, anemic moles, etc.
