Patent ID: 8358886

Claim:
A device comprising a waveguide structure for propagating electromagnetic radiation formed by: a slab ( 10 ) of dielectric material; a first pair of metal plates ( 12 L) and a second pair of metal plates ( 12 R) each pair comprising a first and a second metal plate extending in a propagation direction on opposite faces of the slab; the plates on each face of the slab ( 10 ) being spaced apart laterally with respect to the propagation direction; dielectric cladding material (D) disposed along each of the opposite faces of the slab and having a refractive index less than the refractive index of the slab, and a plurality of plugs ( 14 ) of dielectric material each plug extending alongside an inwardly-facing edge of a respective one of the four metal plates ( 12 L, 12 R), the refractive index of each of the dielectric plugs being greater than the respective refractive indices of the slab ( 10 ) and the cladding material, the device further comprising input means for injecting electromagnetic radiation into the slab to propagate in said propagation direction in a zone defined by and between the four metal plates.