High-power laser light causes various thermal effects in tissue that are used in medicine.
When tissue is irradiated with a laser, a certain proportion of the light is absorbed, depending on the type of tissue and wavelength. This mechanism is used to make therapeutic use of the laser energy introduced. The absorption coefficient describes the probability with which irradiated light is absorbed, and its reciprocal value is the mean free path length that a photon travels in the tissue until it is absorbed.
A distinction is made between various thermal laser applications: