Neodymium Alloy Yttrium Laser

    (Oh, and I suffered 2 years ago with this material, I decided to lay it out and close the gestalt.)

    Jedi swords?

    Personally, I am a supporter of natural ways to become more beautiful (sports, dancing, yoga, positive, normal nutrition, etc.), but at the same time I understand that there are cases where quick and effective intervention is necessary, so I undertook to talk about the laser device , which helps to make "everyone blush and nicer," as in a fairy tale. More precisely, about the principle of its work - I hope that after this publication the process of interaction between the laser and living tissue will become more clear.

    The introductory part presents some materials from the field of anatomy, without which it is not easy to understand the purpose of the laser. The introduction also addresses the issue of protecting the eyes from laser radiation. In the second part, there is a description and principle of operation of the 3 systems that are present in the Synchro Play DEKA device.


    Bit of theory
    Principle of operation Synchro Play DEKA

    Bit of theory

    Skin types

    There are 5 types of skin that doctors share on optical characteristics. Depending on skin type, penetration depth and laser type are selected.

    About the difference of phototypes
    1. Celtic. Such people have delicate, milky white skin, often with freckles, red or very fair hair, and blue or green eyes. The formation of pigment in the skin of such people is insignificant, they quickly burn and practically do not sunbathe.

    2. Nordic, Aryan. The skin of such people is fair, there are few or no freckles at all, fair eyes, fair, light blond, or brown hair. The tan does not go well, but a slight shade of the sun still remains.

    3. Dark European. Such people have brown or gray eyes, dark blond or brown hair. Lightly dark skin without freckles, tans easily.

    4. Mediterranean or southern European.People of this type have dark olive skin without freckles, dark eyes and dark hair. People of this type sunbathe well, almost without sunburn.

    5. Indonesian or Mid-East. They have very dark skin without freckles, their hair is dark, their eyes are dark, their skin tans quickly without burning.

    6. African American. They have very dark skin, black hair and eyes. Never burns. When carrying out cosmetic procedures, people with this skin phototype need to be careful and trust only to professionals, because when performing hair removal, such skin can give the effect of hyperpigmentation.


    Hair growth stages

    Human hair growth depends on many factors, such as age, gender, body weight, metabolism, hormones, ethnicity, medication and other factors. Be that as it may, hair growth takes place in three stages:

    Anagen, catagen and telogen
    1. Anagen - a period of active hair growth, its duration is from 2 to 6 years. With age, the duration of the anagen phase decreases.

    2. Katagen - stage of regression. Atrophy of the hair papilla occurs, as a result of which the cells of the hair bulb, devoid of nutrition, stop dividing and are keratinized. The duration of the catagenic stage is 1-3 weeks.

    3. Telogen - a period of rest or rest of the hair. Mechanical removal of hair in the telogen stage always entails the onset of the anagen stage, that is, the hair begins to grow again.

    Typically, in healthy people, approximately 80-90% of the hair is in the anagen stage, 1-2% is in the catagen stage, and 10-15% is in the telogen stage.


    Types of Lasers Used in Medicine

    A lot of time has passed since the idea to direct a laser at a person for medical purposes (1960s), and this direction has yielded significant results and has been approved by doctors and cosmetologists. The commercial use of lasers in cosmetology began in the mid-90s, and this was preceded by 20 years of experimental research in this direction. The first article was published by a group of authors from Massachusetts General Hospital (conducting the world's largest medical research programs) in 1998.

    In cosmetology, the following types of lasers are most often used:

    • Ruby laser: affects only light skin and dark hair, the absolute effect occurs after repeated use.
      The first laser type presented (1960), the wavelength is 694.3 nm, the pump source is a flash lamp.

    • Alexandrite laser: in comparison with ruby, it is characterized by high speed and power, it is able to remove hair on dark skin in the shortest possible time. Wavelength - adjustable in the range from 700 to 820 nm. The pump source is a flash lamp, laser diodes. For continuous operation, an arc mercury lamp.

    • Diode laser: has a deep penetrating ability, which allows you to get much better results after hair removal, but the hair removal procedure itself is carried out at a relatively low speed. Diode lasers are the most common in the world. The wavelength depends on the material and structure of the active region: from near UV to mid IR.

    • Neodymium laser: acts even on relatively fair hair and dark skin, penetrates deep into the skin. One of the most common high power lasers. Usually operates in a pulsed mode (fractions of nanoseconds). Often used in combination with a frequency doubler. Known designs with quasi-continuous radiation. The wavelength is 1.064 μm. Pump source - flash lamp, laser diode


    Laser Safety Levels and Safety Glasses

    “Dad, what will happen if I shine a laser pointer in the eye of a lion when the trainer stuck his head in his mouth?”

    A laser pointer (whose power is 1-20mW) is fun to play with a cat , but it is not recommended to shine in her eyes. Some hooligans blind pilots with more powerful (500 mW) pointers. 1-10 W lasers burn a balloon or a cap from a marker. What will happen from a laser with a power of 125 or 150 watts?


    Worldwide, the danger (or safety?) Of lasers is divided into several classes:

    imageClass 1.Lasers and laser systems of very low power, not capable of creating a level of exposure hazardous to the human eye. Radiation from Class 1 systems does not present any danger even with long-term direct observation by the eye. In many countries, class 1 also includes laser devices with a laser of higher power, which have reliable protection against the exit of the beam outside the enclosure.

    Class 2. Low-power visible lasers that can cause damage to the human eye if you specifically look directly at the laser for a long period of time. Such lasers should not be used at head level. Invisible emission lasers cannot be classified as class 2 lasers. Typically, visible lasers with a power of up to 1 milliwatt are classified as class 2.

    Class 2a. Lasers and laser systems of class 2a, located and fixed in such a way that the beam does not get into the human eye during proper operation is excluded. This class is used only in some countries.

    Class 3a.Lasers and laser systems with visible radiation, which usually do not pose a danger if you look at the laser with the naked eye only for a short period of time (usually due to a blinking eye reflex). Lasers can be dangerous if you look at them through optical instruments (binoculars, telescopes). Usually limited to 5 milliwatts. In many countries, higher-end devices in some cases require special authorization for use, certification, or licensing. International classes 2 and 3a approximately correspond to Russian class 2.

    Class 3b.Lasers and laser systems that are hazardous when viewed directly from the laser. The same applies to specular reflection of a laser beam. A laser belongs to class 3b if its power is more than 5 milliwatts. In Russia, they roughly correspond to class 3.

    Class 4. Lasers and laser systems of high power, which can cause severe damage to the human eye with short pulses (<0.25 s) of a direct laser beam, as well as a mirror or diffusely reflected beam. Lasers and laser systems of this class can cause significant damage to human skin, as well as have a dangerous effect on flammable and combustible materials.

    The Synchro Play DEKA, which we’ll talk about today, has security class 4, therefore, you need to be very careful.


    The peculiarity of laser radiation is that it can get into the eye with closed eyelids, even because of the angle, and at the same time you may not notice it at all. Light to light is different, and below is the behavior of various wavelengths when it enters the eye.

    The penetration of light with different wavelengths into the eye:


    1. Ultraviolet light with a wavelength of less than 350 nm, incident on the eye, is absorbed by the cornea of ​​the eye. The consequence of exposure to high power of light at these wavelengths is damage leading to destruction of the cornea or the formation of cataracts.

    2.The light perceived by the retina is in the visible wavelength range (380 - 780 nm). Because the human eye is sensitive to light, people have developed natural defense mechanisms. When the light seems too bright, i.e. the power density exceeds the threshold for eye damage, we automatically turn away and close our eyes (i.e., a response or a blink reflex). This automatic response is effective for radiation power up to 1 mW. At higher powers, too much energy will be absorbed by the retina before we blink, it can lead to irreversible damage.

    3.The near infrared range (780 - 1400 nm) is the most dangerous for the human eye, because we do not have natural protection from it. The eye will feel the radiation incident on the retina only after irreparable damage has already been done.

    4. Infrared radiation in the range of 1400 - 11000 nm is absorbed by the surface of the eye and does not reach the retina. This leads to tissue overheating and burning, or destruction of the cornea. However, this happens only at significantly higher powers than those that are dangerous to the retina.

    To the cosmetic procedure did not end at the ophthalmologist, use sunglasses of the 80th level:

    Laser flashes are so powerful that they penetrate even lowered eyelids. Therefore, patients put on special deaf metal glasses.

    Glasses for the operator. For each type of laser, glasses are selected with a specific filter that transmits the maximum amount of visible light, but blocks the light at the laser wavelength. Ease of use with laser safety glasses depends on the VLT (visible light transmission) parameter.

    The attenuation of the light by the filter in the visible spectrum is determined by the said VLT. It is determined by its relation to a standard light source and evaluated according to the spectral sensitivity of the eye to daylight. If the measured VLT value is less than 20%, then the user must ensure that there is additional lighting at the workplace. With low VLT and poor lighting, we can expect that our eyes can adapt to what is called night vision. In this case, color vision will be limited and the range of sensitivity of the eyes will shift towards shorter wavelengths.

    Mechanisms of laser action on organic tissues

    imageLaser hair removal is based on the principle of "selective photothermolysis" - the selective absorption of light by various biological structures: the hair pigment - melanin , which is concentrated in the shaft and the hair follicle, is capable of absorbing light waves of a certain length (the optimal range is 700-800 nm). As a result of the action of laser radiation, melanin, absorbing the energy of light, heats up and destroys neighboring matrix cells (hair germ region) and blood vessels that feed the hair follicle. A few weeks later, the hair shaft with the dead "root" falls out.

    Part of the hair follicles is in a dormant state (about 10-15%) and 80-90% is in active growth. For maximum hair removal (90-100%), a series of hair removal procedures is needed with an interval of 20-45 days, depending on the individual hair growth rate. The number of procedures depends on the type and power of the laser system.

    Skin type affects the absorption of waves of a certain length, therefore, there are graphs and tables of correspondence of the skin phototype and type of laser / IPL.

    More on effects on various tissues

    IPL emits waves of different lengths that are scattered. The tip of the hair is used as a conductor of heat to the hair follicle.

    Alexandrite laser emits light of a certain wavelength. It penetrates deeper into the skin than the IPL and this allows you to direct heat into the hair from all sides and surfaces.

    YAG laser does not focus on melanin. It affects the entire area, and thereby destroys the hair follicle.

    Exposure to excessive pigmentation with a laser


    Excessive amounts of melanin lead to rapid sunburn and age spots. The laser emits a small amount of heat that penetrates the skin. Excess melanin absorbs heat and collapses, age spots thinning, become like a scattering of small spots. Small particles of melanin are recognized by the skin as unnecessary and go outside with sweat. The remaining particles separate from the skin, leaving it smooth and clean.

    Laser effect on wrinkles


    With age, the skin produces less collagen, resulting in wrinkles and wrinkles. The laser emits low-power heat to the skin, stimulating the skin cells, respectively, they wake up and start the production of collagen. Newly made collagen begins to move upward towards the skin surface, resulting in improvements. Collagen production increases and is evenly distributed over the skin, resulting in a smoother texture, smaller pore size, and a reduction in the size of wrinkles, wrinkles and skin tightness.

    Laser exposure to unwanted veins


    Due to improper functioning of the veins, some blood vessels become visible through the skin. The laser penetrates the skin safely and is absorbed by these vessels, destroying them and thereby putting the veins in order and heals them. The vessels that are exposed first become blurred and can darken, and then are removed naturally and the skin takes on a natural color.

    Synchro Play DEKA

    My acquaintance with medical lasers began with this device. A product of Italian production, combines three sources:

    Alexandrite laser - 755 nm

    Neodymium laser (Nd: YAG) - 1064 nm

    IPL - pulsed light system

    I will tell you about them in more detail.

    Alexandrite Laser

    Alexandrite is a natural stone, the most valuable chromium-containing variety of the chrysoberyl mineral (BeAl 2 O 4 ). The cost of natural alexandrite varies from $ 5,000 to $ 37,000 per carat. It is synthesized in laboratory conditions by the method of zone melting .


    imageAlexandrite laser belongs to the class of solid-state lasers. Impurities of Cr +3 ions are 0.01–0.04% in BeAl 2 O 4 crystal.

    The structure of energy levels is similar to the structure of energy levels of a ruby ​​laser.

    It was first applied in 1973 with a wavelength of 680 nm. A little later, we came up with a way how this laser can be tuned to other wavelengths (720-800 nm).

    The Alexandrite laser was the first laser on the market to include wavelength tuning.

    The diagram on the left shows the principle of laser reconfiguration.

    Wavelength - 755 nm
    Frequency - 3 Hz
    Power - 125 W

    The principle of the alexandrite laser

    Before using therapy, you need to remove hair from the surface. The laser beam penetrates the skin safely, being converted to heat in melanin, heating the hair shaft. Heat destroys or weakens the follicle and the hair shaft loses touch with the follicle. Hair falls out, and the absence of a follicle means that the hair will not grow back.


    This is how nozzles look for regulating the depth of penetration of a laser beam:

    Neodymium-doped yttrium aluminum laser (Nd: YAG, Y 3 Al 5 O 12 )

    Nd: YAG - aluminum-yttrium garnet (Y 3 Al 5 O 12 ) doped with neodymium ions (Nd).


    imageNeodymium lasers can operate both in continuous and in pulsed mode. Pulse modes differ in the nature of the generation of laser radiation. In free generation, the pulse duration is usually equal to the lifetime of the upper laser level (about 250 μs, depends on the concentration of neodymium), the pulse is a set of spikes with a duration of up to hundreds of nanoseconds. In Q-switched mode, the duration can vary from a few nanoseconds to microseconds.

    First demonstrated at Bell Labs in 1964. At present, they are used in such areas of medicine as ophthalmology, oncology, dermatology, dentistry and surgery.

    On the left is a diagram of the energy levels of a neodymium laser)
    Wavelength - 1054 nm
    Power - 150 W

    Operating principle
    imageAt the time of the flash of the pump lamp, the atoms of the active element go into an excited state and emit photons. Until the atom has moved from the excited state, the photon entering it knocks out another photon, while the coherence, wavelength, polarization, and phase of these photons will be exactly the same. Thus, the active element amplifies the light, but it is not a laser yet, in order to produce a laser, generation is necessary.

    To start the generation, you need to provide feedback. This is achieved by using mirrors. A blank mirror returns more than 99% of the radiation, an output mirror returns about 90% of the radiation, while the output will be only 10% of the radiation, the efficiency is low. This is due to the fact that if less radiation is returned, then there will be no generation. In any oscillator, which is actually an amplifier, where the output signal is input, it is necessary that the gain exceeds the loss factor, otherwise there will be no generation. For example: when a microphone is brought to the speaker (for example, in karaoke) a strong “howl” appears, this means that feedback was provided in the system and the gain exceeded the loss.

    The principle of neodymium laser exposure

    Before the procedure, the skin surface is cleaned of hair. The laser beam penetrates deep under the skin and heats the entire space. Heat destroys or weakens the follicle and the hair shaft loses its connection. Hair falls out and no longer grows.


    IPL - Intense pulsed light


    IPL is a technology used in medicine for various skin rejuvenation procedures. It is based on the generation of a light beam with different wavelengths (515 - 1200 nm) and the use of various light filters to affect certain tissues. The main difference from the laser is that IPL uses incoherent and non-monochrome radiation.

    Five interchangeable filters (spectral range of wavelengths: 500-950, 550-950, 650-950 nm)

    The area of ​​the working spot of the nozzle is 6.2 cm 2

    Depth of penetration of the beam depending on the filter:



    Beauty is a very interesting topic, in which the physical aspect is only part (depending on the source, from insignificant to dominant). There are interesting psychological phenomena related to the perception of beauty: for example, surrounded by friends, a person is perceived as more beautiful. Another example is related to the fact that men are more likely to forgive beautiful women, and women are more willing to forgive less attractive women. People prefer more attractive candidates when hiring.

    - My dear, I went to a procedure where a solid state aluminum-yttrium laser doped with neodymium ions, diode-pumped, in the Q-switching mode, with quasi-continuous coherent light will affect melanin in the anagen stage.
    - image

    UPD regarding terminology:

    I read your article“ Yttrium-Alumina Laser with Neodymium Doping. ”
    For some time I have been engaged in the synthesis, research, and modification of compounds with a garnet structure ( The term alloying is more applicable to metals. When it comes to single crystals / glasses / ceramics, in the specialized literature, the words activated or doped (co-doped if there are several dopants) are usually used.
    "Synthesized in laboratory conditions by the zone melting method." The zone melting method is used either to purify single crystals or to grow them.Synthesis involves the process of formation of new compounds, growing - the reconstruction of the structure without the formation of new compounds.
    “Neodymium doped yttrium aluminum laser” is a laser based on yttrium aluminum garnet activated (or doped) with neodymium ions (YAG: Nd). First, the main compound is indicated, and then the dopant.
    "Solid-state aluminum-yttrium." At nu YAG cannot be liquid, gaseous, or in a plasma state. He is always solid. Solid-state is another word. It would be more correct to write “a diode-pumped laser based on yttrium aluminum garnet activated by neodymium ions”.

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