Laser Parameters That Affect Results
Several wavelengths of laser energy have been used for hair removal, from visible light to near-infrared radiation. These lasers are characterized by their wavelength, measured in nanometers (nm):
| Argon: 488 nm (Turquoise/Cyan) or 514.5 nm (Cyan) (no longer used for hair removal) |
| Ruby laser: 694.3 nm (Deep Red) (no longer used for hair removal; only safe for patients with very pale skin) |
| Alexandrite: 755 nm (Near-Infrared) (most effective on pale skin and not safe on darker skin at effective settings) |
| Pulsed diode array: 810 nm (Near-Infrared) (for pale to medium type skin) |
| Nd:YAG laser: 1064 nm (Near-Infrared) (made for treating darker skin types, though effective on all skin types) |
| IPL, intense pulsed light: 810 nm (Not a laser but used for hair removal) (for pale to medium type skin) |
Pulse width (or duration) is an important consideration. Longer pulse widths may be safer for darker skin, but shorter pulse widths are more effective in disabling hair follicles. Repetition rate is believed to have a cumulative effect, based on the concept of thermal relaxation time. Shooting two or three pulses at the same target with a specific delay between pulses can cause a slight improvement in the heating of an area. This may increase the "kill rate" for each treatment.
Spot size, or the width of the laser beam, affects treatment. Theoretically, the width of the ideal beam is about four times as wide as the target is deep. Hair removal lasers have a spot size about the size of a fingertip (8-18mm). Larger spot sizes help laser light penetrate deeper and make treatments faster and more effective.
Fluence or energy level is another important consideration. Fluence is measured in joules per square centimeter (J/cm²). It's important to get treated at high enough settings to heat up the follicles enough to disable them from producing hair.
Epidermal cooling has been determined to allow higher fluences and reduce pain and side effects, especially in darker skin. Three types of cooling have been developed:
- Contact cooling: through a window cooled by circulating water or other internal coolant
- Cryogen spray: sprayed directly onto the skin immediately before and/or after the laser pulse
- Air cooling: forced cold air at -34 degrees C
Read more about this topic: Laser Hair Removal
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