Theory of the interaction of infrared radiation with solids

A transport equation for electron-avalanche breakdown, including large- and small-quantum effects, was developed, checked by two derivations, compared with previous results, solved by three methods (numerical solution of partial-differential equation, casting into eigenvalue differential equation form, approximate intuitive solution), applied to simple models and to cases of practical interest, and compared with gas-breakdown results. Large-quantum processes, including interband transitions and various processes in which photons are absorbed simultaneously with processes which allow momentum conservation will be considered. Intraband processes (valence band to final conduction band plus intraconduction band, for example) as well as the usual interband process in two-photon absorption-coefficient calculations gave good agreement (factor of 0.5 to 4) with Harvard experimental results without adjusting parameter values. Calculations showed that including a linear temperature dependence of the optical absorptance of metallic or dielectric reflectors gave much higher temperatures and damage susceptibilities in general than for the case of temperature-independent absorptance and gave thermal runaway in several interesting cases.