Page 167 - Mike Murphy's Blog Posts

skin epidermal melanin and in blood. This means that if you fire 532nm light energy at black skin you will likely damage both the epidermis and the superficial capillaries. In fact, this occurs in all skin colours too! I have observed this phenomenon in Caucasian skin (my own!) using a Q-switched Nd:YAG laser at 532nm - read my report here.
Conclusion
The above data seems to suggest that the 532nm wavelength is the 'best' choice for both melanin and blood vessels. However, this wavelength is strongly scattered in the dermis which significantly reduces its penetration. This makes it pretty useless when tackling hair follicles - they are too deep! Nor is it useful for deeper blood vessels. This is why the longer wavelengths tend to be used for these targets. However, 532nm is an excellent choice for epidermial pigmented lesions such as freckles, age and liver spots.
The above describes how well different wavelengths are absorbed in two main targets in the skin, but it does not describe the whole situation. For example, I have not mentioned scattering much here - that's for another day (You might want to read my report on this topic here). Nor have I mentioned 'useful' fluence - the fluence that actually does the task in hand. I'll cover that topic another time.
I hope this helps you to better understand how the light we fire at skin, from our lasers, interacts with those targets.
Mike.
Mike’s Blog Posts 167