SURFACE-MODE AT ISOTROPIC-UNIAXIAL AND ISOTROPIC-BIAXIAL INTERFACES

The surface mode that propagates along the interface bet seen isotropi c and uniaxial materials, as first suggested by M. I. D'Yakonov [Sov. Phys. JETP 67, 714 (1988)], is quantitatively characterized in terms o f (1) the range of crystallographic orientations for which the mode pr opagates, (2) its propagation constant beta, and (3) its field profile s. Previous studies have considered only uniaxial materials whose opti c axis is in the plane of the interface. We show that a surface mode c an also propagate along the interface between isotropic and arbitraril y oriented uniaxial or biaxial materials. This mode is also quantitati vely characterized. For the biaxial material oriented so that its opti c axes lie in the plane of the interface, it is shown that this surfac e mode is guided over a greater range of propagation directions and th at the Light is confined more tightly than for any isotropic-uniaxial interface of comparable birefringence. In addition, it is shown that. the surface modes that occur at isotropic-uniaxial interfaces combine to form a new type of hybrid mode in uniaxial slab waveguides (two int erfaces). The resulting modes differ from conventional slab waveguide modes in that (1) they are composed entirely of inhomogeneous waves an d (2) at. most two of these modes can exist regardless of the waveguid e thickness. (C) 1998 Optical Society of America.