Nonlinear generation of the fundamental and first harmonic of a periodic surface profile under the action of s-polarized laser radiation

The authors have developed an analytic nonlinear theory which describes the formation of periodic structures on a surface subjected to s-polarized laser radiation. In this paper they investigate the processes by which laser-induced evaporation of material and photochemical etching of semiconductors can generate periodic surface profiles, and rigorously derive dynamic equations which describe the linear and steady-state nonlinear oscillatory regimes for generation of the fundamental and first spatial harmonics of these profiles. They study the relative roles of intermode and intramode nonlinearities, as well as the effect of reactive nonlinearities which are due to interference between the fields of resonance surface electromagnetic waves and those of second-order diffraction. Their work clarifies the importance of topological nonlinearities caused by rescattering of temperature waves or concentration waves of electron-hole pairs by the generated profile. The authors show that under the action of laser irradiation it is possible to create a profile for which absorption of radiation incident on the surface reaches 100%