2. Principles of Laser–Tissue Interaction

When laser light interacts with biological tissue, several physical processes may occur depending on the tissue type, the laser's wavelength, energy, pulse duration, and exposure time. The four main mechanisms of interaction are:

• Absorption: photons are taken up by molecules (chromophores) within the tissue;
• Scattering: light is redirected as it passes through tissue;
• Reflection: A portion of the incident light is bounced back at the surface;
• Transmission: Some light passes entirely through the tissue.

These interactions are not mutually exclusive and often occur simultaneously, affecting how deeply the laser penetrates and what diagnostic or therapeutic effects are produced. Understanding and controlling these processes is essential in designing safe, effective laser-based diagnostic tools (Barsom et al., 2016; Zafar et al., 2021).