Wavelength (Nanometer / nm)

Wavelength is the length of a light wave, measured in nanometres (nm). In aesthetics it is the single most important spec on any laser or light device, because it determines how deep the energy travels and which target (chromophore) it heats.

Nanometre (nm)

Unit

Depth & target

Determines

400–10,600nm

Typical range

Why Wavelength Decides Everything

Light behaves as a wave, and the distance between two peaks of that wave is its wavelength, expressed in nanometres (nm). Every laser, IPL and LED device is defined first by its wavelength, because that number controls two things at once: how deep the energy penetrates the skin, and which structure it is preferentially absorbed by.

As a rule, longer wavelengths reach deeper. Visible light around 400–500nm (blue) stays superficial; 600–700nm (red) reaches the dermis; near-infrared at 800–1064nm penetrates deeper still toward hair follicles and subcutaneous tissue; and 10,600nm (CO2) is absorbed almost entirely by surface water for ablation. The wavelength must also match the absorption peak of the intended chromophore—melanin, haemoglobin or water—so the energy lands on the target and spares everything else.

For an equipment buyer, wavelength is the first filter: a 755nm Alexandrite excels on light skin and fine hair, a 1064nm Nd:YAG is the safe choice for dark skin, and a multi-wavelength platform buys versatility across indications.