Laser Physics

The word LASER is actually an acronym for Light Amplified by Stimulated Emission of Radiation. Lasers used for hair removal operate in the visible, near-infrared, or infrared portion of the electromagnetic spectrum.

For the purpose of laser hair removal, there are a few key vocabulary words to understand. Different lasers operate at different wavelengths on the electromagnetic spectrum. The ruby laser, for example, operates at 694 nm, whereas the Nd:YAG operates at 1064 nm. This is important because, in general, the longer wavelength of the Nd:YAG penetrates the skin deeper and makes it safe to treat all skin types including darker tones. The ruby laser can only treat fair-skinned people, but may be more effective in treating fine hairs. Other popular lasers in between these two are the Alexandrite, at 755 nm, and the Diode, at 810 nm. These lasers may share mixed properties. The wavelengths of all these lasers determine the target chromophore, which is melanin in the hair follicle.

Pulse duration is the length of time a set amount of energy is delivered to the tissue targeted. Longer pulse durations allow the skin to heat up slower and is safer for darker skin tones. Alternatively, shorter pulse durations can be more effective for treating fine and light colored hair. Most lasers vary greatly as to the pulse durations available.

Fluence is the amount of energy delivered to a given area. It seems self-explanatory that higher fluences will achieve better hair removal results, but again risk thermal damage. Operator experience is extremely important in achieving effective results without side effects with all lasers.

Spot size determines the area to be treated. Lasers vary widely on the spot sizes available for use. At least 3-5 mm is required for effective hair removal. Spot sizes determine the depth of penetration. In general, the larger the spot size, the greater the depth of penetration. This means more effective hair removal and less thermal damage. Smaller spot sizes are still useful because the operator can use higher fluences. The larger the spot size of the laser beam, the more fluence must be used to achieve the same result. Lasers have limits as to the amount of energy that can be used with the larger spot sizes. Another advantage of the larger spot size is the ability to treat larger areas of the body very quickly.

Based on the scientific principles, one can see that there is not one laser that can treat everyone. Also, the ability to manipulate the settings on each laser is an extremely fine balance. An experiences physician with extensive laser training should be sought after to perform laser hair removal.