How it works
At 10600nm the chromophore is water, and skin is mostly water. The beam is absorbed within the first tens of micrometres and vaporises tissue where it lands. Fractional mode splits that energy into a grid of microscopic columns and leaves bridges of untreated skin between them. That's why fractional wounds close in days, not weeks. Manstein and colleagues described the principle in 2004; the wavelength logic sits in our note on selective photothermolysis.
Here's the trade-off nobody spells out at a trade show. Energy per microbeam sets column depth. Density sets how much surface you ablate. Shah and Alam split it plainly: deeper zones from higher fluence suit acne scarring and tightening, shallower and denser coverage suits fine photodamage and dyspigmentation. Push both up and you're running full-field ablation with extra steps, recovery bill included. Our manuals put the focused spot near 0.25mm and maximum penetration at up to 2mm. Coverage proportion shrinks the treated area while density holds: 1x1cm at 6x6 set to 1/2 treats 0.5x0.5cm, still 6x6. Deep and sparse for boxcar scarring. Shallower and denser for texture.
Fire adjacent columns back to back and heat stacks. Scatter them and each cools first. Our manuals are blunt: never scan an area more than three times, never overlap graphics. Remodelling runs for months, so judging a scar at week two is a mistake. How far you push is a patient question, and our note on reading Fitzpatrick skin types says where to stop.