Electromagnetic-wave surfaces in absorptive uniaxial crystals. I. Cones ofzero birefringence and cones of equal absorption for isonormal waves

The existence conditions of the circular cones of propagation directions fo r isonormal electromagnetic waves of two independent branches for weakly ab sorptive optically uniaxial crystals with the same phase velocities (which corresponds to the zero birefringence) have been studied, and the opening a ngles of these cones have been determined. It is shown that these cones are formed solely due to absorption. The circular cones of directions, which c orrespond to the equal absorption coefficients of two independent isonormal waves, were also studied in a similar way. The regions of existence of the se cones are described in the explicit analytical form. The dependence of t he opening angles of these cones on the components of the complex tensor of the inverse electric permittivity of crystals is also analyzed. It is show n that these two types of cones cannot coexist for one crystal. (C) 2000 MA IK "Nauka/Interperiodica".