Page 173 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Long-Pulsed Nd:YAG Laser – Threshold fluences
The absorption of 1064nm light by melanin is relatively low compared with the above three devices (see Figure 96). As a consequence, a higher fluence is required from Nd:YAG lasers to achieve the same level of temperature rise in the hairs.
Body area
Threshold fluence (J/cm2)
Upper lip
24.5
Chin/arms
44.5
Arm pits/legs
51.0
Bikini
59.7
Table 32 - Threshold fluences for Nd:YAG lasers
The threshold at the skin surface for this laser is approximately 24.5 J/cm2, assuming a 10ms pulsewidth. The absorption by melanin of this wavelength is much weaker compared with the other hair removal systems. This explains why such relatively high fluences are required to achieve results. However, the absorption in the dermis is also very low which is why the Nd:YAG laser penetrates so deeply into the skin.
Figure 97 – Threshold fluences across the body for four devices. The thresholds for diode lasers and the ‘averaged’ IPL output are almost identical.
________________________________________________________________________ 173 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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