Theory of operating:
The Q-switched ND: YAG laser delivers light of specific wavelengths with high energy which are absorbed by the pigment in the tattoo and result in a shockwave. The shockwave shatters the pigment particles, releasing them from their encapsulation and breaking them into fragments small enough for removal by the body. These tiny particles are then eliminated by the body. Since this specific wavelength can only be absorbed by pigment particles, no injury to skin and normal tissues will occur.

Before-after pictures: