Tailoring of modal losses in anisotropic 2D material ribbons by regulating material absorption

Abstract

In plasmonic guided waves, material absorption is generally an unwanted shortcoming that degrades the quality of plasmon modes by greatly curtailing their propagation distance. In this work, we explore the general features of the modal properties supported by 2D anisotropic materials and elucidate how the material’s in-plane anisotropy can offer a previously untenable level of control or tailoring over plasmonic waveguide design. In particular, we find that utilizing the in-plane anisotropy of anisotropic 2D materials in the conductivity of ribbon films, it is possible to significantly manipulate the modal loss of the plasmonic guided modes by increasing the material absorption of the 2D materials. The physical root cause of this behavior is control over the various electric field components within the film by utilizing the material dispersion of the anisotropic film. This control allows for the ability to manipulate at will, for a wide a range of structure parameters and wavelengths, the net field within the ribbon arising from the interplay between the two edge modes, which constitute the film edges. The findings thus unlock beneficial capabilities offered by using natural 2D anisotropic materials such as black phosphorous in the design of active/passive nano-scale circuits. Furthermore, when these effects are employed in gain media composed of 2D materials, the ability for the realization of low modal loss plasmonic modes concomitant with the presence of substantial material absorption can introduce a new design paradigm that promises novel and enhanced functionality.