Technology guide
Fluence and laser parameters
Fluence, pulse duration, frequency, spot size: the settings of a hair removal laser explained simply.
Fluence
Fluence is the amount of energy delivered per square centimetre of skin, expressed in J/cm². The higher it is, the stronger the effect on the follicle, but the greater the risk of burns. It is set according to skin type, wavelength and hair type, and must never exceed what the manufacturer specifies.
Pulse duration
Expressed in milliseconds, it determines how the heat is distributed. A longer pulse heats more gradually and more deeply, which spares dark skin; a shorter pulse concentrates the energy. Fluence and pulse duration are adjusted together.
Frequency
In hertz, this is the number of shots per second. A high frequency speeds up treatment, particularly in scanning mode; a lower frequency allows more time for cooling.
Spot size
A large spot covers large areas quickly and penetrates better; a small spot is more precise for the face or contours. The total energy of a shot depends on the fluence and the surface area of the spot.
A rule of caution
Several passes at moderate fluence are safer than a single pass at maximum fluence. Start with cautious settings and adjust according to how the skin reacts.