Tattoo removal: a colorful challenge requiring multiple laser wavelengths

The trend for “getting inked” and the increase in "tattoo regret"

The trend for “getting inked” as a form of self-expression continues to be popular in many parts of the world. One in eight Europeans have a tattoo, with the figure doubling among young adults. The USA is another tattoo hotspot. In 2021, around 26% of Americans had a tattoo, according to research by Statista, with 17% having more than one.

While many people who have a tattoo are happy with their decision, the upward trend inevitably means a corresponding increase in “tattoo regret”, leading to people seeking ways to get rid of unwanted body art. In fact, the tattoo removal market is forecast to increase significantly in the next five years, driven by personal changes in taste and lifestyle, as well as increasing availability and innovation in laser tattoo removal technologies. As an indicator, Imarc estimates the value of the global tattoo removal market will be US$ 392.43 million by 2027, exhibiting a compound annual growth rate (CAGR) of 7.70%.

Health factors are also influencing the rise in people seeking tattoo removal procedures. Some skin disorders, such as sarcoidosis, can be exacerbated by tattoos and magnetic resonance imaging (MRI)-based burns can be caused by metal-based ink tattoos. Then, there’s concern about color tattoos. In January 2022, the European Chemicals Agency banned thousands of chemicals used in ink for color tattoos in response to concerns over allergic reactions and a possible cancer link. This has brought colorful tattoos into the spotlight as people reevaluate the risks.

Erasing color tattoos

However, erasing full color tattoos is a much more complicated procedure than removing “traditional” black ink tattoos. Laser wavelengths are a key factor. By delivering short duration, high-power pulses of light energy, lasers in tattoo removal devices break ink particles in the skin. Different colors absorb and reflect light differently, so if the ink doesn't absorb the light sufficiently, it won't fragment. This all depends on the wavelength of the laser beam.

The most popular wavelengths for Q-switched (QS)lasers used in the tattoo removal industry are:

• 1064 nm wavelength Nd:YAG laser for black inks
• 532 nm wavelength, frequency doubled Nd:YAG laser for red inks
• 694 nm wavelength ruby laser for green, black and blue inks
• 755 nm wavelength alexandrite laser for black, green, yellow, and blue inks
• 785 nm wavelength Ti:Sapphire laser for green, blue and purple inks

In a study on the removal of full color tattoos (Bernsteinet al., 2018), a 785 nm picosecond-domain laser demonstrated safe and effective removal. The 785 nm wavelength proved particular active with purple, blue and green inks. The research provides useful intelligence on the relationship between laser wavelength and pigment color.

To remove a full color tattoo effectively you need at least three laser wavelengths. A common laser combination is 1064 nm (Nd:YAG), 532 nm (frequency doubled Nd:YAG) and 755nm (alexandrite). There are a few alternative wavelengths to the 755 nm, such as 785 nm (Ti:Sapphire) and 694 nm (Ruby). Therefore, multi-wavelength systems are required to enable aesthetic and medical practitioners to treat color inks tattoos. These powerful and versatile machines incorporate photonics technologies to achieve effective and safe color tattoo removal.

The role of Pockel cells in laser modulation

One of the most important photonic components for success in laser tattoo removal is the Pockels cell, particularly in relation to wavelength. These devices work according to the Pockels effect, also known as the linear electro-optic effect, where applying a voltage across a nonlinear crystal affects the polarization of the light transmitted. Pockels cells effectively act as a Q-switch to modulate the laser beam. Meanwhile, the choice of crystal optics used in the device determines the all-important wavelength.

The best crystals are those that utilize proprietary crystal growth, fabrication, polishing and coating techniques under one roof to ensure quality and performance. Potassium dideuterium phosphate crystals, known as KD*P, are among the most effective in laser tattoo removal technology. They can operate across a wide wavelength range (300–1100 nm), from near infrared (NIR) to ultraviolet (UV). Defect free and low stress crystals also enable the high energy and short pulses required for successful laser tattoo removal.

As trends change towards even more vibrant colors, neon pigments and metallic inks, further innovation will be required to ensure people have safe and effective options to remove unwanted tattoos. Research and development (R&D) to optimize the laser wavelength to particular ink colors continues. This includes refining the properties of the crystal optics used in tattoo removal technologies to continuously improve results. You could say, with the correct choice, aesthetic laser manufacturers have a crystal-clear solution to the colorful problem of tattoo removal.

If you’d like to talk through the topics in this article and seek advice about photonics technology for tattoo removal systems, get in touch.