The essential elements of lasers that determine its interaction with matter are as follows:
Pulse rate and duration
Laser Beam Interact with tissues in four ways
A portion of the incident beam may be reflected on the surface without penetration or interaction with tissues.
A portion of the light may be transmitted through the tissues unattenuated.
A portion of light may be absorbed by the tissues.
Remaining light may penetrate the tissues and be scattered without producing noticeable effect.
The extent of the interaction will be proportional to the wavelength of absorption of the particular wavelength by tissue. Tissue elements that exhibit a high co-efficient of absorption for particular wavelength or speed of light energy are called chromophore.
Tissue effects of laser irradiation
When laser is absorbed by tissue four types of reaction occurs:
Photochemical interaction includes biostimulation which describes the stimulatory effects of lasers on biochemical and molecular process that normally occur in tissues such as healing and repair.
In Photothermal interaction laser light energy absorbed by the tissue substances and molecules becomes transformed into heat energy which produces the tissue effect. Thermal effects are largely wave length dependent because the amount of heat generation in tissues is determined by extent of preferential absorption of beam.
Photomechanical and Photoelectrical Interaction
Photo disruption, photo dissociation, photo Plasmolysis, photo acoustic are used to describe mechanical and electrical interaction.