How Tattoo Removal Lasers Work
LASER is an acronym the represents Light Amplification by the Stimulated Emission of Radiation. Lasers emit monochromatic (single color/wavelength) light through a process called stimulated emission in a narrow beam or series of pulses.
A bright, quickly-flashing light source called a flashlamp is used to excite atoms in the gain medium – a material with special properties that allows it to amplify light. These gain media can be solids, liquids, or gases; in tattoo removal lasers they are most often crystals. When the atoms of the crystal receive energy, the electrons become excited and move to a higher orbital level.
These electrons will not stay in this excited state without end, and when they return to their ground state and drop to a lower orbital level, a photon will be emitted. A photon is a bundle of energy that has a specific frequency or color that exactly matches the distance the electron falls. Visible light is made up of photons that our eyes are able to absorb and in collections to perceive as images.
The gain medium of a laser is selected because of its ability to produce wavelengths of light that can do work. A wavelength that can be absorbed can cause an object to heat up, like when a black shirt in summer absorbs all of the sun’s light and causes the wearer to be hot. The white shirt would reflect light back away from the wearer, and cause them to be relatively cooler.
Wavelengths for Tattoo Removal
Tattoo removal lasers produce specific wavelengths of light that have been proven to be absorbed by certain colors of tattoo ink. When this energy is applied for the right length of time, at the right level of energy, and in the proper wavelength, the tattoo ink will heat up to such an extent that it will cause the ink to shatter into tiny pieces and made possible for removal by the body’s immune system.
The 1064 nanometer (nm) wavelength is produced by the Nd:YAG crystal, and is absorbed well by dark colors of tattoo ink, including black, brown, and purple. This crystal is made of Yttrium Aluminum Garnet doped with Neodymium, and when excited the electrons of this substance travel 1064 nanometers and give off photos of that frequency (in the near-infrared part of the electromagnetic spectrum).
A laser that produces a beam of 1064nm photons can convert, though a manipulation commonly called “frequency-doubling” (or equivalently “wavelength-halving” given the inverse relationship between wavelength and frequency). The resulting 532nm wavelength is well absorbed by red, orange, and yellow tattoos. Most tattoo removal lasers, like the Astanza Duality, use the 1064nm and 532nm wavelengths to remove tattoos, but they are generally unable to remove blue and green tattoos beyond some limited amount.
A synthetic ruby crystal can be used to produce a wavelength of 694.3nm, which is well-absorbed by blue and green tattoo ink. The ruby laser, when combined with an Nd:YAG laser containing 1064nm and 532nm wavelengths, can be effective at removing virtually every color of tattoo, making the Astanza Trinity the only truly-effective multi-color tattoo removal laser on the market.
Q-Switching
A laser can produce the right wavelengths of light, but unless this energy is applied for the right length of time and with sufficient power, the desired effect will not be achieved. Tattoo ink can be notoriously difficult to shatter, and only recently have lasers been able to produce sufficient fluence (energy or power) to remove dark and bright tattoos without unattractive side effects like scarring.
Astanza lasers uses a technique called q-switching to produce the high peak powers necessary to shatter ink and quick pulse necessary to avoid scarring. Q-switching involves using an electronically gated mirror and other components to allow light to escape the laser’s optical cavity for only a fraction of a second. In the case of our tattoo removal lasers, these pulses last only a few nanoseconds (billionths of a second), allowing for a very powerful pulse to be emitted, sufficient to heat tattoo ink to several hundred degrees centigrade for this tiny fraction of a second.
Without active q-switching techniques, peak powers cannot be generated to shatter tattoo ink, which is one of the reasons that low to medium end lasers cannot effectively remove tattoos. Other factors that play a role in the power of the laser are the size of the optical cavity, quality of the amplifier, and precision of the optics that deliver the energy from the optical cavity to the hand piece.
The other key factor in effectively shattering ink is the length of time that a target is heated. If heated for too long, scarring can result. As the targeted structure (tattoo ink, hair, etc) of a laser is heated, if a certain temperature is reached in a certain time, the target will shatter or be destroyed. Beyond a certain length of time, however, the excess heating will leak to surrounding tissue and cause thermal damage and scarring. Astanza lasers uses laser physics to get rid of the risk of scarring.
Astanza q-switched lasers are designed and manufactured specifically for tattoo removal. Hair removal lasers operate with much longer pulse widths, and if they are used for tattoo removal, the result in most or all cases will be scarring without effective removal of tattoo ink.
