Peculiarities of material heating at oblique incidence of pulsed laser radiation

An analysis of material heating under oblique incidence of pulsed radiation on the front target surface is carried out. It is shown that there is a definite incidence angle for which the highest heating temperature of a target surface, exceeding the heating temperature at normal radiation incidence is achieved. The last is true for some materials and in particular for crystals with an ion type of chemical bond (LiF). A solution of the heat equation for a plate forms the basis of the analysis. The target is the 0.1 cm plate made of monocrystalline LiF located in the atmosphere of quiet air. The ''excessive'' heating is shown to take place in ultraviolet visible and infrared regions of the spectrum. It is necessary to fulfil the following conditions to achieve the maximum ''excessive'' heating: the laser radiation pulse duration is 10-3-10-9 s; the radiation wavelength for a monocrystal with an ion type of chemical bond is 5-100 μm (infrared region); the laser radiation beam incidence angles are 30-70 deg (usage of lasers with a radiation beam divergency of several degrees is possible). Usage of the radiation, the electric field intensity vector of which lies in the plane of incidence of radiation (p-wave), is preferable. The ''excessive'' heating phenomenon may be used for the increase of the efficiency of thermal effect of the pulsed laser radiation upon materials