Laser Materials Interactions

Understanding the capabilities and limitations of laser machining requires the knowledge of physical processes occurring during the laser beam interactions with materials. When the electromagnetic radiation is incident on the surface of a material, various phenomena that occur include reflection, refraction, absorption, scattering, and transmission (Fig. 2.1). One of the most desirable and important phenomena in the laser processing of materials is the absorption of the radiation. Absorption of radiation in the materials results in various effects such as heating, melting, vaporization, plasma formation, etc., which forms the basis of several laser materials-processing techniques (Steen 1991). The extent of these effects primarily depends on the characteristic of electromagnetic radiation and the thermo-physical properties of the material. The laser parameters include intensity, wavelength, spatial and temporal coherence, angle of incidence, polarization, illumination time, etc., whereas the materials parameters include absorptivity, thermal conductivity, specific heat, density, latent heats, etc. The interaction of laser with material is a complex interdisciplinary subject and requires knowledge from several branches of physics. This chapter briefly explains the important laser–material interactions and their effects which are relevant in the laser machining and fabrication of materials.