Multimode phenomena in semiconductor-clad dielectric optical waveguide structures

Semiconductor-clad optical waveguides possess unique properties which arise from the periodic coupling effect between the lossless modes of the dielectric waveguide and the lossy modes which are supported by the thin semiconductor layer. This paper presents a detailed analysis of this mode structure showing mode conversion as a function of cladding thickness. The analysis predicts that several types of mode may exist for certain guide thicknesses, depending on the magnitude of the absorption in the semiconductor. The combined effects of waveguide coupling and loss are determined and illustrated in devices using silicon claddings.