Page 106 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Wavelength
Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
How do hair removal systems compare?
The first thing to understand is that diode, alexandrite and Nd:YAG lasers are different! And these are quite different compared with IPLs.
So, let’s first look at those differences:
1. Wavelength
2. Pulsewidths
3. Fluences
4. Absorptions
5. Skin colours
6. Cooling
7. Power densities
All the lasers used for laser hair removal typically use infra-red wavelength – that’s any wavelength longer than 700nm – which are all invisible to the human eye. IPLs can output a wide range of wavelengths, up to 1200nm. But, for hair removal, they are usually filtered so that only the range about 600 to 1200nm is actually utilised. Some systems also filter out the top end of this range so that they are restricted to between 600 and 900nm, typically.
Device
Table 13 – The wavelengths output by most hair removal systems
These wavelengths are all absorbed by melanin (see Figure 43) and can penetrate deep into the dermis. (We often see online comments saying that “IPL light energy doesn’t penetrate as deeply as lasers” – this is just gibberish!). Note that there other diode systems which may output a 900nm wavelength, plus there are some systems which combine the diode with an alexandrite and an Nd:YAG laser, into one unit.
But the penetration depth is not the only important factor when considering wavelength. We must also think about how much of that energy will actually be absorbed by the target – follicular melanin (see below).
________________________________________________________________________ 106 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022
Wavelength (nanometres)
Diode
808, 810
Alexandrite
755
Nd:YAG
1064
IPL
400 - 1200