Compact optical waveguides based on hybrid index and surface-plasmon- polariton guidance mechanisms

Abstract

Surface-plasmon-polariton (SPP) waveguides made of materials available in nature have, in general, been found to suffer from very high absorption loss when light confinement is beyond diffraction limit. In this paper, the possibility of combining both the conventional index-guiding and the SPP-guiding mechanisms together into one single waveguide is being explored. Such waveguides, expectedly, inherent the low-loss feature of all-dielectric waveguides as well as the superior mode field confinement possessed by SPP waveguides. By using experimentally ready materials, it is theoretically shown that compact metallodielectric waveguides can be designed with a ∼500×500 nm2 core size around the 1550nm telecommunication wavelength. The examined waveguides can be interpreted as a gap SPP waveguide with an inner dielectric core. Compared to pure SPP waveguides, such hybrid waveguides have a comparable mode field size, but with significantly lower loss (∼0.05 dB/μm for either quasi-TE or quasi-TM operation). Therefore they can be potentially deployed for a range of integrated photonic applications.