Page 118 - Blog Posts v1

epidermal basal layer and capillaries are more likely to be damaged – I wrote about this in a letter to the British Journal of Dermatology (click here) a few years ago.
Thirdly, the 1064nm wavelength has some advantages over the others – it penetrates deeper than the rest and it doesn’t interact strongly with melanin or haemoglobin meaning that it is less damaging than the others.
Fourthly, the 532nm frequency-doubled wavelength form a QS Nd:YAG laser is actually a combination of both 532 and 1064nm This is simply because the frequency-doubling crystal is never 100% efficient – most tend to be around 70 to 80% efficient. So, a beam of 532nm energy will be around 75% 532nm and 25% 1064nm.
This means that a fluence of, say, 10 J/cm2, will be made up of 7.5 J/cm2 of 532nm light and 2.5 J/cm2 of 1064nm light. So, 10 J/cm2 of 532nm light energy is not equivalent to 10 J/cm2 of 1064nm light! Plus, the 532nm will interact more with the melanin and blood vessels.
Conclusion
This has probably just confused most of you reading this! The fact is, it is not trivial. Changing wavelengths is not a straightforward choice.
We never know the absorption coefficients of the inks we’re treating (unless you own a spectrophotometer...). Hence, we can never know which is the most appropriate wavelength to apply.
Perhaps the best way forward is to try different wavelengths on the colours we are treating, at different fluences, to see which responds best. This might help to improve the overall result, but it will take a little longer...
Hope this helps (a bit!!), Mike.
Mike’s Blog Posts 118