the branch of physical optics that studies the effect on solid media of fluxes of optical radiation (light) so intense that the radiation can result in destruction of the integrity of the medium. Power optics developed after the appearance of lasers when intense light fluxes came into use for optical processing of materials and when it became necessary to devise shaping and transmitting optical systems that do not lose efficiency in the presence of high power densities. In optical technology, the term “power optics” is sometimes applied to the elements of an optical device—such as mirrors, lenses, and prisms—that are designed to operate in dense radiation fluxes.
Power optics investigates the processes of the release of energy in transparent (weakly absorbing) or absorbing media that are exposed to intense light fluxes; it also analyzes the results of such exposure. By analogy with mechanical strength and electric strength, the concept of radiation strength is introduced to characterize the efficiency of optical materials, such as glasses, crystals, and coatings. The radiation strength is equal to the specific power or energy of the optical radiation flux at which irreversible changes begin appearing in the substance. The radiation strength increases as the exposure time or the irradiated area of the material decreases. Moreover, the radiation strength is determined not only by the absorption coefficient but also by nonlinear processes in the substance (such as the self-focusing of light) and by microscopic nonuniformities of its structure.
For absorbing materials, such as metals, narrow-band semiconductors, and ceramics, determinations are made of the radiation parameters—specific power, energy, and duration—at which various kinds of destruction occur. Melting, vaporization, and cracking are examples of such destruction. Here, as in transparent media, the change in the characteristics of a substance during exposure to laser radiation is of great importance. For example, the reflection and absorption coefficients may change, or absorption may appear in the products of the light erosion of a substance. The radiation parameters determined in this manner and the conditions of exposure of the substance to the radiation are used in developing laser devices for the optical processing of materials—for example, for welding, cutting, the making of small holes, and the fabrication of microelectronic components.
REFERENCESDeistvie izlucheniia bol’shoi moshchnosti na metally. Edited by A. M. Bonch-Bruevich and M. A. El’iashevich. Moscow, 1970.
Aleshin, I. V., Ia. A. Imas, and V. L. Komolov. Opticheskaia prochnost’ slabopogloshchaiushchikh materialov. Leningrad, 1974.
Ready, J. Deistvie moshchnogo lazernogo izlucheniia. Moscow, 1974. (Translated from English.)
A. M. BONCH-BRUEVICH [23–1088–]