How Laser Tattoo Removal Works
The current state of the art in laser tattoo removal involves the use of q-switched lasers. The concept is based on “selective photothermolysis” and “photoacoustic effects.”
The ink from a tattoo is generally located within the dermis layer of the skin. The ink may be black, red, or almost any color. A laser light of a particular wavelength, such as 1064 nanometers, is differently absorbed by the particular ink in the tattoo than by the surrounding skin. Thus, the ink particles within a tattoo absorb much more laser energy than the surrounding normal skin. This is referred to as selective photothermolysis.
This difference in absorption though, is not enough to perform successful tattoo removal. The energy must be delivered so fast that it “shatters” the ink particles rather than just heating them up slowly. This is where “q-switching” comes in. The q-switch is like a super-fast shutter on the laser that allows only brief shots of laser light to come out at a time. When something is heated or cooled extremely quickly, it doesn’t have time to expand or contract properly, and so it cracks. This is the photoacoustic effect. If a non-q-switched laser of the proper wavelength were used to treat the tattoo, it would typically cause a burn in the area of the tattoo. This is why laser hair removal is not safe over a tattoo.
These are the two main elements of the mechanism of laser tattoo removal. There are other subtleties that are also important, such as the wavelength of the laser light, the size of the spot, the uniformity of the beam, and the amount of total energy applied to each burst of the laser.
