Low-loss and high-performance mid-infrared plasmon-phonon in graphene-hexagonal boron nitride waveguide

In this article, we propose a class of high-performance and low-loss waveguide by exploiting the hybridization of the plasmon-phonon modes through the coupling graphene with hexagonal boron nitride (hBN). It is found that inserting an ultra-thin hBN layer with hyperbolicity behavior between graphene and a thin low-index substrate leads to squeezing a light into hBN, enabling a low-loss light propagation as compared with a traditional graphene/substrate plasmonic waveguide. Furthermore, the results show that by choosing appropriate values for physical parameters of the proposed waveguide as well as the chemical potential of graphene, a low-loss and high-performance optical plasmon-phonon mode in the mid-infrared range can be achieved simultaneously. In particular, by increasing the chemical potential from 0.2 to 1 eV, 12- and 6-fold enhancement for propagation length (Lm) and figure of merit, respectively, is achieved with the optimized proposed waveguide. The results presented here are very helpful for designing low-loss nanophotonic devices.