Materials Response to High Power Energy Lasers(A Short Course—PartⅣ)

摘要

A complete understanding of laser interaction with materials is still a matter of trials and adjustments.The real physical processes of laser beam interaction(drilling,cutting,welding,or being used as a directed energy weapon application)with materials are very complex.Problem of laser interaction with materials presents many difficulties,both from modeling as well as from experimental sides.One would expect a reasonable description of the main phenomena occurring during laser interaction,but this is complicated because many of physical processes equally contribute to the development of conservation equations,producing drawback because of a great complexity of the equations to be solved.In most instances,this leads to formulation of a model needed to be solved numerically.A lack of pertinent experimental data to compare with,forces one to simplify some equations and use previous analytical and computational work done in this field.In Part IV here,we cover the absorption coefficient,which can be derived from the material’s dielectric function and conductivity,determines the absorption of light as a function of depth.However,the specific mechanisms by which the absorption occurs will depend on the type of material.In general,photons will couple into the available electronic or vibrational states in the material depending on the photon energy.In insulators and semiconductors,the absorption of laser light predominantly occurs through resonant excitations such as transitions of valence band electrons to the conduction band(inter-band transitions)or within bands(inter-sub-band transitions).In this part we cover all the aspect of the“Mathematical of Laser Absorption in Metals”that fits into this part of our suggesting short courses in different parts so far.