We propose a highly efficient graphene-on-gap modulator (GOGM) by employing the hybrid plasmonic effect, whose modulation efficiency (up to 1.23 dB/μm after optimization) is ∼12-fold larger than that of the present graphene-on-silicon modulator (∼0.1 dB/μm). The proposed modulator has the advantage of a short modulation length of ∼3.6 μm, a relatively low insertion loss of ∼0.32 dB, and a larger modulation bandwidth of ∼0.48 THz. The physical insight is investigated, showing that both the slow light effect and the overlap between graphene and the mode field contribute. Moreover, an efficient taper coupler has been designed to convert the quasi-transverse electric mode of conventional silicon waveguide to the hybrid plasmonic mode of GOGM, with a high coupling efficiency of 91%. This Letter may promote the design of high-performance on-chip electro-optical modulators.
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/μm, 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 (A eff /A 0 < 1/1000), which significantly improves the light-graphene interaction. A large modulation efficiency of 4.05 dB/μm 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.
We present an effective scheme to improve the modulation capacity in graphene-based silicon modulator by employing the double slots configuration with hybrid plasmonic effects. Two modulators, i.e., metal-insulator-metal and insulator-metal-insulator configurations have been demonstrated, showing that the double slots design can significantly improve the modulation efficiency. The obtained modulation efficiency is up to 0.525 dB/μm per graphene layer, far exceeding previous studies. It can be found that the light-graphene interaction plays a pivotal role in the modulation efficiency, whereas the height of metal has profound influence on the modulation. Our results may promote various future modulation devices based on graphene.
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