Hemoglobin

Haemoglobin is the protein in red blood cells that carries oxygen and gives blood its colour. As a chromophore it has clear absorption peaks—most usefully in the green-yellow range (around 540–580nm) and again at 1064nm—which is exactly what vascular treatments exploit.

When a wavelength matched to haemoglobin is delivered, the energy is absorbed inside the blood vessel, heating and coagulating it so the body can reabsorb it. This is how IPL, KTP and Nd:YAG devices clear broken capillaries, diffuse facial redness, rosacea, spider veins and some vascular birthmarks. Larger, deeper vessels favour the deeper-penetrating 1064nm; fine superficial redness responds to shorter wavelengths and IPL.

For a clinic, vascular work is a high-demand, high-margin indication—knowing that haemoglobin is the target clarifies which wavelengths and devices to invest in.