1) Pulsewidth is an important characteristic. Some published studies suggested that longer pulsewidths are safer in darker skin.

2) Wavelength is an arguable factor. Longer wavelengths considered to be safer in darker skin.

There are several lasers with different wavelengths of laser energy:

• Argon: 488 or 514.5 nm
• Ruby: 694 nm
• Alexandrite: 755 nm
• Pulsed diode array: 810 nm
• Nd:YAG: 1064 nm

3) Spot size, or the width of the laser beam, is an important factor that affects treatment. Theoretically, the width of the ideal beam is about four times as wide as the target is deep. Most lasers have a round spot about the size of your little finger (8-10 mm).

4) Fluence or energy level is another important characteristic. Fluence is measured in joules per square centimeter (J/cm2).

5) Repetition rate has a cumulative effect, based on the concept of thermal relaxation time. Producing two or three pulses at the same target with a particular break between pulses can lead to a slight improvement in the heating of an area.