  The spontaneous decay of a V-type three-level atom placed in a
negative-refractive-index waveguide is analyzed. We find that in thin
waveguides, highly efficient surface guided modes are supported, which do not
occur in positive index waveguides. In addition, at low absorption, the mode
density and thus spontaneous emission into particular regular guided modes is
enhanced by several orders of magnitude as compared to regular dielectric
waveguides. The asymmetries between emission into the different modes and the
enhancement of particular guided modes allow to induce strong
spontaneous-emission interference between transitions with orthogonal
transition dipole moments.
