Dependence of light transmission through human skin on incident beam diameter at different wavelengths

Hair Reduction Using a Scanning 800 nm Diode Laser

“…This effect depends on spot diameter, with smaller spots having greater scattering losses 2 . One study has shown that when measuring 810 nm light transmittance 3.4 mm below the skin surface, the transmittance of a 6 mm and 4 mm diameter light beam will be reduced by 30% and 60%, respectively, as compared to the light transmission of a 12 mm diameter incident beam 26 . The biopsies, however, indicate that regardless of what accepted photon propagation models might predict about spot size limitations, even with relatively small 4 and 5 mm spots, “enough” energy penetrates to the base of the follicle (bulb) to achieve significant and effective temperature increases in many cases.…”

Scatter‐limited phototherapy: A model for laser treatment of skin

“…The scatter of light in tissue was measured by Zhao and Fairchild [10]. As shown in Figure 2, they measured the transmission of Fig.…”

“…For water near room temperature, k ¼ 0.6 W/m8C, and r ¼ 1 g/cm 3 , and C p ¼ 4.2 J/g8C. [10]. The incident beam was a parallel beam of light.…”

Dissecting Cellulitis Treated with the Long-Pulsed Nd:YAG Laser

“…Another important principle in laser hair removal is that deeper penetration of radiation is achieved with longer wavelengths 8 . The 1,064‐nm wavelength of the Nd:YAG laser can penetrate deep within the dermis to target follicular melanin.…”