PERCEPTION of LASER TECHNOLOGY
Let us analyze the main characteristics of the devices using the example of lasers for hair removal
WHICH LASER IS BETTER?
Fluence (energy flux density) F=J/cm2.
Fluence (energy flux density), J/cm2 is the most important parameter on which the effectiveness of laser hair removal depends. This parameter means how much laser energy is transmitted per unit of skin surface during the procedure. The larger it is, the more energy will be delivered to the hair follicle. The fluency is directly related to the energy and power of the laser device, but is not an analog of these parameters, but depends on the spot area.
When choosing a laser device, one should be interested not in its energy, but in its fluence (pulse energy), as well as the range in which this fluence can be changed. An epilation laser with a low maximum fluence value may not be effective, for example, for removing coarse hair.
Pulse duration, ms.
It takes some time for the heat to spread from the heated hair shaft to the follicle stem cells. This means that lasers with a short pulse are not suitable for laser hair removal, or rather, the use of such lasers will allow you to burn out the hair shaft, but may leave the stem cells of the follicle intact. Typically, laser hair removal uses pulses with a duration of 10 to 100 or more milliseconds. Moreover, short impulses are suitable for thin hair, and long impulses are for thick, coarse hair.
Spot size, mm
It is an important parameter. With an increase in the spot size, the proportion of scattered light decreases, and due to this, the penetration depth increases, and the effectiveness of the epilation of hair lies deeper. Also, the large spot size allows you to process large areas at high speed. However, even though a small spot size requires the use of a larger fluence, it cannot be completely abandoned, since it is needed for epilation in hard-to-reach areas.
WHICH LASER IS BETTER?
For laser hair removal, alexandrite, diode and neodymium lasers are used. Each manufacturer claims that their type of laser is the "gold standard". However, when choosing a laser, you should trust the data of clinical studies.
ALEX laser (755 nm)
The radiation of the alexandrite laser (755 nm) is very well absorbed by melanin, therefore alexandrite hair removal is effective, but its effect is mainly pronounced when hair removal in patients with phototypes I–III, on fair skin. When removing hair in patients with IV-VI phototypes (on dark skin), these lasers are practically not used, since the melanin in the epidermis is very hot and this can lead to the development of complications such as burns and hyperpigmentation. In addition, the penetration depth of the alexandrite laser is smaller than that of the diode (800–810 nm) and neodymium Nd:YAG lasers.
Nd Yag (1064 nm) & DIODE laser (808 nm)
The neodymium Nd:YAG laser generates radiation with a wavelength of 1064 nm, at which melanin is absorbed relatively poorly, but at the same time the penetration depth is maximum. Neodymium Nd:YAG lasers are widely used in countries where the majority of the population is made up of patients with very dark and black skin (V-VI phototypes). Diode lasers with a wavelength of 800–810 nm are the most versatile. And although their radiation is absorbed by melanin slightly worse than the radiation of alexandrite lasers, they are widely used due to the fact that they can be effectively applied to the skin of any phototype. And the essence of rays with such a wavelength is not just an effect on melanin, but a possible coagulation of the blood vessels that nourish the hair, which allows you to effectively remove blond hair.