Abstract: The existence conditions and waveguiding properties of new hybrid, TE-dominant waveguide modes of properly tailored waveguides consisting on ultrathin films cladded by a positive birefringent crystal are analyzed. The results show that the existence conditions of such waves strongly depend on the waveguide parameters. Accordingly, the related guided-to-radiated wave transition holds promise for switching applications requiring a strong sensitive dependence on the material refractive index values.