Embodiments disclosed herein include waveguides. In an embodiment, a waveguide comprises a conductive shell and a first ridge within the conductive shell. In an embodiment, the first ridge extends away from the conductive shell. In an embodiment, the waveguide further comprises a first core over the first ridge, where the first core comprises a first dielectric material with a first permittivity. In an embodiment, the waveguide may further comprise a second core embedded in the first core, where the second core comprises a second dielectric material with a second permittivity that is greater than the first permittivity.