00:14Thechoice of pulse duration in fractional photothermolysis is not a matter of speed—it is a matter of the thermal relaxation time of the target chromophore.
00:52Whenusing an Er:YAG laser at 2940 nm, the absorption in water is approximately 12,800 cm⁻¹—which is extremely high. This means minimal penetration depth and maximum precision, but also rapid conversion of energy into heat.
01:48Inpractice, this translates to the following set of parameters for standard resurfacing of the periorbital region:
Wavelength 2940 nm (Er:YAG)
Pulsdauer 250 µs
Fluenz 5.5 J / cm²
Spot 5 mm
Pass 2 (overlap 10%)
02:34Ifthe pulse duration is increasedto about 1 ms, the thermal diffusion time of the tissue is exceeded—and thus the fractional nature is lost…