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The wavelength is not important. Melanin absorbs across the full visible spectrum, plus a chunk of the near infrared too.
It turns out that the pulsewidth is not so important either, as long as it’s between around 5 and 50ms. But even this restriction disappears as the fluence is increased.
The type of light doesn’t really matter either. It’s merely a method for transferring energy into the follicles. Laser - IPL? Not important!
There is no real evidence that the blood supply is important. Some people think that we need to coagulate the vessels supplying the follicle. The physics doesn’t agree. Red light is mostly reflected by blood, yet we always use red light to kill follicles. Plus, those vessels are relatively deep - we don’t typically use sufficient fluence to get enough energy at that depth, even if they did absorb strongly. But, in fact, melanin blood absorbs about 10 times as much as blood at the Nd:YAG wavelength (1064nm).
Hope this helps, Mike.
Mike’s Blog Posts 103
