Electromagnetic-wave surfaces in absorptive uniaxial crystals. II. Cones of specific ordinary waves and cones of extreme absorption

The conditions are established under which extraordinary electromagnetic wa ves in absorptive optically uniaxial crystals have a group velocity paralle l to the wave normal (which corresponds to the definition of ordinary waves ). It is shown that absorption can result in the formation of a circular co ne of propagation directions of such specific ordinary waves, which can be formed only in nontransparent crystals. If the directions of wave propagati on corresponding to the extreme directions of the refractive-index surface are symmetric (i.e., located along the optical axis or normally to it), abs orption can cause the transformation of the refractive-index maximum into t he minimum. The circular cones of the directions of wave propagation, for w hich the absorption coefficients of electromagnetic waves have extreme valu es, are also studied. (C) 2000 MAIK "Nauka/Interperiodica".