Highly Efficient Graphene-Based Optical Modulator With Edge Plasmonic Effect

We report a highly efficient graphene-based modulator by using an edge plasmonic effect in this paper. The modulation efficiency of the proposed modulator can be as large as 1.58 dB/<italic>μ</italic>m, which is several times larger than that of previous reported modulators. By enhancing the gap plasmon mode and the edge plasmonic effect in a well-designed diagonal waveguide, a wedge-to-wedge SPP mode is strongly confined in both horizontal and vertical directions in terms of a small mode area <inline-formula><tex-math notation="LaTeX"> $({{A_{eff}}/{A_0} < 1/1000})$</tex-math></inline-formula>, which significantly improves the light-graphene interaction. A large modulation efficiency of 4.05 dB/<italic>μ</italic>m has been obtained after geometry optimization, which is the best values reported in our knowledge. The physical reason for the improvement is explored. We find the sharpness of the waveguide edges has strong impact on the field enhancement and modulation efficiency. Geometry optimization is made to further investigate the enhancement mechanisms and modulation capacities. Our results may promote the development of active nanophotonic devices incorporating two-dimensional materials.