Alexandrite laser and other apparatus used in hair removal. Practical comparison. Part III / Diode laser hair removal
3. Diode laser hair removal.
Until relatively recently, diode lasers
was not at all suitable for laser hair removal.
Just do not had technological level.
For this reason alone we can say that
beauty salons that claim the "gold standard "for hair
removal with respect to a new technique in hair removal - diode laser
hair removal - at least not correctly received and unprofessionally
toward their clients the same...
For reference, laser hair removal with
alexandrite laser is well-proven in the removal of unwanted hair
since 1996 (now 15 years old!), and the equipment used by this method
improves with each year, making the procedure more comfortable and
Recall that the wavelength diode laser
is 810 nm and the alexandrite laser wavelength is 755 nm.
The increase in wavelength leads to an
increase in energy absorption in tissues surrounding the hair and
reduce the absorption energy of the pigment melanin in skin and hair
(see schedule of absorption).
Schedule of hemoglobin absorption (1)
and melanin (3):
But even without taking into account
the fact that the increase in wavelength leads to an increase in
energy absorption surrounding tissues of the hair look at the main
disadvantage of diode lasers in laser hair removal in present.
At the present stage the development of
this technique is the low peak power.
Peak power lead! manufacturer of diode
lasers is 500 watts.
The diode laser in fact it is more
powerful, but it cannot be compared with the capacity of solid state
of Alexandrite laser for hair removal, which develops 2000 watts,
producing 40 J for 20 ms!
A natural question arises - why is such
power of alexandrite laser needed?
The answer is to most effectively heat
the hair follicle germ band before his injury (and as a consequence -
no further growth) without concomitant damage to surrounding skin.
In laser medicine, there is such an
important concept, as the thermal relaxation of tissue (TRT), which
is the time at which target-tissue (in this case, the hair follicle)
gives off heat into the surrounding tissue (in this case it is skin).
For the hair follicle, this time is
from 10 to 35 ms (depending on skin photo type, hair color and
If the pulse duration will be longer
this time, a significant portion of the pulse energy will dissipate
in the surrounding tissues, causing unnecessary heat.
The energy of the light beam = Power *
In other words - the shorter the
duration of pulse, the lower its energy.
According to the formula, if the laser
power is insufficient to give the necessary energy is possible only
with very long pulses, much longer than the thermal relaxation time
of the follicle as a result and cause overheating of the surrounding
That is what often happens when a diode
laser hair removal in the form of very noticeable! soreness
Unlike diode lasers, high power of
Alexandrite laser system for laser hair removal allow depending on
the type of skin and hair (if necessary) to establish individual
minimum pulse duration is not losing energy, which completely
eliminates the risk of overheating the surrounding tissue and thus
To be continued ...