Long-range all-dielectric plasmonic waveguide in mid-infrared

Abstract In this paper, we introduce the modal analysis of hybrid plasmonic waveguides in the mid-infrared region. In our plasmonic waveguide, the metal is replaced by doped silicon allowing for low-loss, subwavelength confinement of optical modes that can be easily integrated with standard silicon technology. In addition, our waveguide characteristics can be easily tuned along the wavelength by changing the doping concentration of the doped silicon layer. Manipulating the dimensions of the waveguide, we can effectively change the propagation distance and the mode confinement. The simulation results show a maximum propagation distance of 220 µm and modal area of 5–500 times smaller than the diffraction limit area. Moreover, the wavelength dependence of the effective indices of the hybrid structures modes around the doped silicon resonance was investigated. Our results showed that our structures exhibit anomalous dispersion and can support slow and fast light. Also, a comparison has been made between our hybrid structure and the conventional insulator–metal–insulator (IMI) waveguide with metal replaced by our doped silicon. This comparison shows that our hybrid structure is a compromise between the modal area and the propagation distance of the IMI structures.