Tattoo removal works by 'blasting' the particles within the ink apart, which are then removed from the body by its own defence mechanisms.
The laser produces flashes or pulses of light. The high-energy laser light is absorbed by anything dark - including tattoo ink. The light is simply reflected off normal pale skin without any effect.
When the tattoo ink is hit by the laser, in a tiny fraction of a second the water in the ink is converted to steam, and this breaks down the collagen capsule that is protecting the ink. Once the ink is free, your body's own immune system can start to remove the ink that has been released.
Because the laser energy is so strongly absorbed by dark ink, all the energy is dissipated in the ink nearest the surface. The layers of ink below do not receive much energy, and little ink is released from the deeper layers. This means that you will see some fading of the tattoo as the surface ink is removed by your immume system, but further treatments will be needed to break up the ink in the lower layers. Treatments are usually repeated every four to six weeks.
Professional tattoos can take eight treatment sessions upwards to eliminate, depending on the density of the ink, the colours of ink involved, and your own immune reaction. Amateur can take less although you should see noticable results straight way.