The Physical Difference Between Wavelengths 755 nm, 808 nm, and 1064 nm in Laser Hair Removal.
In laser hair removal, both effectiveness and safety depend on how light of a specific wavelength interacts with the skin's chromophores: mainly melanin (in the hair and epidermis), hemoglobin, and water.Here is the key physical difference between the three main wavelengths:1. Melanin Absorption (the primary target)Melanin has a broad absorption peak in the 600–1100 nm range, but the absorption coefficient decreases as wavelength increases.
- 755 nm (Alexandrite): Very high melanin absorption (about 2–3 times higher than 808 nm). The light strongly interacts with melanin → excellent follicle heating even at relatively low energy.
- 808 nm (Diode): Good absorption — the “golden middle”. Sufficient to effectively heat the hair, but noticeably less than 755 nm.
- 1064 nm (Nd:YAG): Very weak melanin absorption (roughly 10 times lower than 808 nm). The light mostly “passes by” the melanin.
- 755 nm: Penetrates about 1–2 mm. Ideal for superficial follicles (face, fine hair), but poor for deep follicles (legs, back).
- 808 nm: Penetrates 3–5 mm. Optimal for most treatment areas — reaches the hair bulb and bulge.
- 1064 nm: Penetrates 5–7 mm and deeper. Best for thick, deep-rooted hairs and very dark skin.
- 755 nm: Strongly absorbed by oxyhemoglobin → higher risk of vascular reactions and more competition from blood.
- 808 nm: Minimal absorption by hemoglobin and water → very high selectivity for melanin.
- 1064 nm: Absorbed more by water than by melanin → more volumetric heating of the dermis, but very low competition from hemoglobin.
- 755 nm: Excellent for types I–III (light skin), high burn risk on IV–VI (dark skin) because of high epidermal melanin.
- 808 nm: Safe for types I–V, acceptable for type VI with low energy settings.
- 1064 nm: The safest for types IV–VI (dark skin), but requires high energy → more sessions needed.
- Melanin absorption
755 nm — Very high
808 nm — High
1064 nm — Low - Penetration depth
755 nm — 1–2 mm
808 nm — 3–5 mm
1064 nm — 5–7+ mm - Safety on dark skin
755 nm — Low
808 nm — Medium to high
1064 nm — High - Effectiveness on fine/thin hair
755 nm — Excellent
808 nm — Good
1064 nm — Weak - Competition/risk from hemoglobin
755 nm — High
808 nm — Low
1064 nm — Very low - Average number of sessions
755 nm — 4–6
808 nm — 6–8
1064 nm — 8–12
- 755 nm — maximum selectivity for melanin, but shallow penetration and strong competition from epidermal melanin.
- 808 nm — the optimal balance: sufficient melanin absorption + good penetration depth + minimal unwanted absorption by other chromophores.
- 1064 nm — minimal melanin absorption, but maximum penetration → works mainly through bulk/volume heating of tissue.
