Graphene-based Slow Light Waveguides

Slow light has been investigated as a solution to control the optical signal by reducing the group velocity. So far, many techniques have attained slow light, but there generally exists a bottleneck that the bandwidths (w) are small which leads to a large signal distortion. In addition, these waveguides are not dynamically tunable. To solve these problems, we propose two kinds of graphene slow light waveguides with wide band and low dispersion. The main works are as follows:Firstly, we summarize the current researches on slow light waveguide. After comparing various structures reported in the literatures, we find the bandwidths of the waveguides are small and they are not tunable. In order to gain better performance and dynamic adjustability of the waveguide, we suggest graphene as a candidate to build the waveguide. The resent research has reported that graphene can support SPP with an enlarged ng. Based on the dispersion relation presented by the literature, we depict the ng-f curve and demonstrate that an enlarged ng will be achieved when SPP propagates through the graphene sheet, which proves that graphene can propagates slow light.Secondly, for the purpose of obtaining the wideband performance, we decide to add periodical structure to the graphene sheet and use a Finite Difference Time Domain (FDTD) to analyze the slow light performance accurately. Here, we propose a grating graphene waveguide, of which ng=(130±4) and bandwidth w=2THz can be achieved. When the voltage applied to the graphene sheet varies, the slow light performance of the waveguide changes which means,f and w can all be dynamically tuned by electrically modulation.Thirdly, we present a triangle-hole graphene waveguide which is structurally simpler than the grating graphene waveguide, and optimize its performance by adjusting the structure parameters. When the incident resonance frequency f varies from90.15THz to90.75THz, ng remains to be (107±5). Next, the optimization of the slow light capability is successfully done by monitoring each slow light indicator when altering the triangle size, and the results show an extremely large NDBP value of0.96which is much larger than all previous reported results.