Page 139 - Blog Posts v1

B8 - Laser tattoo removal of ink colours - Part 3
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One of my readers, Dan Jackson, asked me about pulsewidth (in a roundabout way) after my recent posts about ink colours (Part 1, Part 2). I had forgotten that the pulsewidth does have an effect on the threshold (minimum) fluences required to instigate the desired response in tattoo ink colours.
A few years ago I did a wee review of tattoo laser treatments through the decades. I found that the fluences typically used were directly related to the pulsewidths (see figure below).
Shorter pulses need less fluence than longer ones, regardless of wavelength. The shortest pulse I could find was used by Ross et.al. with an experimental picosecond laser of duration 35 ps. This was not a commercial system.
They found that they could stimulate a response using only 0.65 J/cm2, whereas a conventional picosecond laser required around 1.0 J/cm2 – current “picosecond” lasers utilise pulsewidths between 350 and 800 ps, according to their manufacturers. (Which means that they are better describes as ‘sub-nanosecond’ since these equate to 0.3 and 0.8 ns...)
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