Page 116 - Mike Murphy's Blog Posts

But.....
And it’s a big but....
When we change the wavelength, we must stop and consider what is also changing. It is not merely a shift in the applied laser light colour. The way the light interacts with the skin’s constituents also changes. If we change from 1064nm down to 532nm, we need to realise that the melanin and blood vessels will also absorb more of the energy. They just do! I made a video describing this too.
If the melanin and blood are absorbing some of this energy, then there is less energy available to reach the tattoo ink. We would need to increase the applied fluence to mitigate. But this could lead to more tissue damage...
So, changing wavelength is not a trivial exercise – we must think about the ramifications of doing so.
How much do the inks absorb?
The above chart shows the absorption spectra for five ink colours – black, green, blue, red and yellow. We can see that black absorbs best out of these colours, but that its absorption drops as the wavelength falls below 700nm.
Green and blue have relatively low absorption from 900nm up, but they peak around 700nm – close to the alexandrite wavelength (755nm).
Mike’s Blog Posts 116