Technical evolution

Even more specialized: two new generation Alexandrite lasers have integrated a technology derived from the discovery of a French researcher, Serge Mordon.

Instead of delivering the energy constantly, the laser astutely delivers the energy intermittently in a sequence of shots spaced of a few milliseconds. The skin has all the time to cool down (it evacuates half the accumulated heat in less than a millisecond). But the hair, with a Thermal Relaxation Time of 10 to 40 milliseconds, keeps storing the heat that cannot be evacuated, so it is stored and the temperature keeps increasing until it reaches the thermal damage threshold.

Explanation: the skin cover, a flat surface, cools down much faster than the cylindrical hair. If you are not convinced, try and pour some soup in a bowl and in a plate and wait to see which of the recipients cools down the first! The lasers, applying this technology based on this physics law of energy dissipation, deliver their fluence by intermittent shots. This succession of short impulses enables an accumulation of heat in the hair until its complete destruction, as well as a cooling of the skin. The epidermis has just the time to cool down before the laser delivers a new impulse, which increases the hair heat, and so on… This process is a real advance in selective photothermolysis.

Patients with slight dark skins and dark hair are the best candidates for laser hair removal

MORE INFORMATION : thermal relaxation time (TRT) is the time necessary for the tissue to diffuse half of the heat received to adjacent tissues. The little melanin grains that colour the skin and the epidermal cells have very short TRT and cool down very fast. By luck, terminal hair have a 10 ms TRT in the stem and a 40 ms TRT in the bulb. With an efficient fluence, the heat stored by large hair during the shot can literally make them explode and expulse them out of the dermis. A short shot duration is used on light skins with thin hair. On tanned, dark or black skins, the shot duration is long.

Personal choice

We use one of the two devices on the market equipped with this system. We are really satisfied by our choice, since the device allows to increase the power transmitted to the skin and to avoid collateral damages. This innovation enables to push the limits of laser hair removal by treating black and tanned skins with a safety margin unknown until then. It enables to envisage the permanent treatment of men backs and to treat blond hair efficiently.

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