Above critical angle ϕ_c, the normalised wave number κ_z is no longer limited by the value of ε_1f, but, in the regions above ε_1f and below the solid curves, the modes are inhomogeneous. The blue areas are the regions where hybrid homogeneous modes occur. The figure shows the decreasing range of θ over which these modes are possible as ϕ increases beyond the value of ϕ_c. The dashed line is the result for the anisotropic substrate where as ϕ changes the change in the graph is undetectable on the scale of the figure.