laser-deep/physics

SPTL depends on a chromophore inside the target that absorbs the chosen wavelength preferentially relative to surrounding tissue. For hair removal, that chromophore is melanin, but three other absorbers in skin — haemoglobin, water, and tattoo ink — become…

Selective photothermolysis (SPTL) is the theoretical foundation of every laser hair-removal device in commercial use, laid down in a single 1983 paper and elaborated in a supporting 2001 generalisation. Understanding SPTL in enough detail to reason about…

The original selective photothermolysis framework required pulse durations shorter than the target's thermal relaxation time (TRT). In hair removal, this produced a tension: the target is not the pigmented shaft (which regrows) but the bulge stem cells and…