2. Principles of Laser–Tissue Interaction

Tissue response to laser light is largely determined by the presence of chromophores—molecules that absorb specific wavelengths. Key chromophores in biological tissue include:

• Hemoglobin (absorbs in the visible range),
• Melanin (broad absorption from UV to NIR),
• Water (strong absorption in mid-to-far infrared).

Laser wavelength selection is thus critical. For example, green and blue lasers (wavelengths around 488–532 nm) are readily absorbed by hemoglobin, making them ideal for visualizing and targeting blood vessels. Near-infrared light (700–1400 nm) penetrates deeper into tissue due to lower absorption and scattering, making it well-suited for imaging subcutaneous structures such as in Optical Coherence Tomography (OCT) or Laser Doppler Flowmetry (LDF)(Albrecht et al., 2013; De Miguel & Martínez, 2023).