A novel terahertz modulator based on graphene is proposed and designed. The device consists of a silicon ridge covered by a graphene sheet. The transmission properties of the proposed structure demonstrate that the introduction of graphene can improve the switching and filtering performance of modulators, and enhance its field confinement capability. In the case of the number of layers, a blue shift can be observed in the center wavelength with increase of graphene layers. Meanwhile, the relationship between the number of layers and the peak of reflection spectra is an inverse proportion function. In addition, we find that the center wavelength is almost unchanged with respect to the different chemical potential, thus the effective refractive indices of the cross section of light propagation direction can be well preserved. These findings will contribute to the research and development of graphene based THz waveguide modulators.

The slot waveguide has attracted considerable attention because of its ability to confine and guide electromagnetic energy at the subwavelength scale beyond the diffraction limit. We propose a novel terahertz slot waveguide structure to achieve a better tradeoff between propagation length and field confinement capacity, the novel waveguide consisting of a two slot structure. The performances of terahertz waveguides were investigated using the finite-element method. The results demonstrated that the hybrid slot waveguide (HSW) provides significantly enhanced field confinement in low index slot regions: more than five times that of traditional low index slot waveguides (LISWs). An optimized HSW structure was achieved by tuning the tradeoff between mode confinement and propagation length. We also showed that its integration in conventional planar waveguide circuits was greatly improved compared with the LISWs, by comparing their crosstalk. The proposed new HSW structure has great potential to enable THz production of compact integration and could lead to true semiconductor-basedTHz applications with high performance.

The emerging field of nanophotonics requires plasmonic devices to be fully compatible with semiconductor fabrication techniques. However, very few feasible practical structures exist at present. Here, we propose a CMOS-compatible hybrid plasmonic slot waveguide (HPSW) with enhanced field confinement. Our simulation results show that the HPSW exhibits significantly enhanced field confinement as compared with the traditional low-index slot waveguides and the hybrid metal dielectric slot waveguides. By controlling the thicknesses of different layers, an optimized HPSW structure with a better tradeoff between field confinement and propagation length has been simultaneously achieved.